includes/db/Database.php

   1 <?php
   2 /**
   3  * @defgroup Database Database
   4  *
   5  * This file deals with database interface functions
   6  * and query specifics/optimisations.
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 2 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License along
  19  * with this program; if not, write to the Free Software Foundation, Inc.,
  20  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  21  * http://www.gnu.org/copyleft/gpl.html
  22  *
  23  * @file
  24  * @ingroup Database
  25  */
  26
  27 /** Number of times to re-try an operation in case of deadlock */
  28 define( 'DEADLOCK_TRIES', 4 );
  29 /** Minimum time to wait before retry, in microseconds */
  30 define( 'DEADLOCK_DELAY_MIN', 500000 );
  31 /** Maximum time to wait before retry */
  32 define( 'DEADLOCK_DELAY_MAX', 1500000 );
  33
  34 /**
  35  * Base interface for all DBMS-specific code. At a bare minimum, all of the
  36  * following must be implemented to support MediaWiki
  37  *
  38  * @file
  39  * @ingroup Database
  40  */
  41 interface DatabaseType {
  42         /**
  43          * Get the type of the DBMS, as it appears in $wgDBtype.
  44          *
  45          * @return string
  46          */
  47         function getType();
  48
  49         /**
  50          * Open a connection to the database. Usually aborts on failure
  51          *
  52          * @param $server String: database server host
  53          * @param $user String: database user name
  54          * @param $password String: database user password
  55          * @param $dbName String: database name
  56          * @return bool
  57          * @throws DBConnectionError
  58          */
  59         function open( $server, $user, $password, $dbName );
  60
  61         /**
  62          * Fetch the next row from the given result object, in object form.
  63          * Fields can be retrieved with $row->fieldname, with fields acting like
  64          * member variables.
  65          *
  66          * @param $res ResultWrapper|object as returned from DatabaseBase::query(), etc.
  67          * @return Row object
  68          * @throws DBUnexpectedError Thrown if the database returns an error
  69          */
  70         function fetchObject( $res );
  71
  72         /**
  73          * Fetch the next row from the given result object, in associative array
  74          * form.  Fields are retrieved with $row['fieldname'].
  75          *
  76          * @param $res ResultWrapper result object as returned from DatabaseBase::query(), etc.
  77          * @return Row object
  78          * @throws DBUnexpectedError Thrown if the database returns an error
  79          */
  80         function fetchRow( $res );
  81
  82         /**
  83          * Get the number of rows in a result object
  84          *
  85          * @param $res Mixed: A SQL result
  86          * @return int
  87          */
  88         function numRows( $res );
  89
  90         /**
  91          * Get the number of fields in a result object
  92          * @see http://www.php.net/mysql_num_fields
  93          *
  94          * @param $res Mixed: A SQL result
  95          * @return int
  96          */
  97         function numFields( $res );
  98
  99         /**
 100          * Get a field name in a result object
 101          * @see http://www.php.net/mysql_field_name
 102          *
 103          * @param $res Mixed: A SQL result
 104          * @param $n Integer
 105          * @return string
 106          */
 107         function fieldName( $res, $n );
 108
 109         /**
 110          * Get the inserted value of an auto-increment row
 111          *
 112          * The value inserted should be fetched from nextSequenceValue()
 113          *
 114          * Example:
 115          * $id = $dbw->nextSequenceValue('page_page_id_seq');
 116          * $dbw->insert('page',array('page_id' => $id));
 117          * $id = $dbw->insertId();
 118          *
 119          * @return int
 120          */
 121         function insertId();
 122
 123         /**
 124          * Change the position of the cursor in a result object
 125          * @see http://www.php.net/mysql_data_seek
 126          *
 127          * @param $res Mixed: A SQL result
 128          * @param $row Mixed: Either MySQL row or ResultWrapper
 129          */
 130         function dataSeek( $res, $row );
 131
 132         /**
 133          * Get the last error number
 134          * @see http://www.php.net/mysql_errno
 135          *
 136          * @return int
 137          */
 138         function lastErrno();
 139
 140         /**
 141          * Get a description of the last error
 142          * @see http://www.php.net/mysql_error
 143          *
 144          * @return string
 145          */
 146         function lastError();
 147
 148         /**
 149          * mysql_fetch_field() wrapper
 150          * Returns false if the field doesn't exist
 151          *
 152          * @param $table string: table name
 153          * @param $field string: field name
 154          *
 155          * @return Field
 156          */
 157         function fieldInfo( $table, $field );
 158
 159         /**
 160          * Get information about an index into an object
 161          * @param $table string: Table name
 162          * @param $index string: Index name
 163          * @param $fname string: Calling function name
 164          * @return Mixed: Database-specific index description class or false if the index does not exist
 165          */
 166         function indexInfo( $table, $index, $fname = 'Database::indexInfo' );
 167
 168         /**
 169          * Get the number of rows affected by the last write query
 170          * @see http://www.php.net/mysql_affected_rows
 171          *
 172          * @return int
 173          */
 174         function affectedRows();
 175
 176         /**
 177          * Wrapper for addslashes()
 178          *
 179          * @param $s string: to be slashed.
 180          * @return string: slashed string.
 181          */
 182         function strencode( $s );
 183
 184         /**
 185          * Returns a wikitext link to the DB's website, e.g.,
 186          *     return "[http://www.mysql.com/ MySQL]";
 187          * Should at least contain plain text, if for some reason
 188          * your database has no website.
 189          *
 190          * @return string: wikitext of a link to the server software's web site
 191          */
 192         static function getSoftwareLink();
 193
 194         /**
 195          * A string describing the current software version, like from
 196          * mysql_get_server_info().
 197          *
 198          * @return string: Version information from the database server.
 199          */
 200         function getServerVersion();
 201
 202         /**
 203          * A string describing the current software version, and possibly
 204          * other details in a user-friendly way.  Will be listed on Special:Version, etc.
 205          * Use getServerVersion() to get machine-friendly information.
 206          *
 207          * @return string: Version information from the database server
 208          */
 209         function getServerInfo();
 210 }
 211
 212 /**
 213  * Database abstraction object
 214  * @ingroup Database
 215  */
 216 abstract class DatabaseBase implements DatabaseType {
 217
 218 # ------------------------------------------------------------------------------
 219 # Variables
 220 # ------------------------------------------------------------------------------
 221
 222         protected $mLastQuery = '';
 223         protected $mDoneWrites = false;
 224         protected $mPHPError = false;
 225
 226         protected $mServer, $mUser, $mPassword, $mDBname;
 227
 228         protected $mConn = null;
 229         protected $mOpened = false;
 230
 231         /** @var Array */
 232         protected $trxIdleCallbacks = array();
 233
 234         protected $mTablePrefix;
 235         protected $mFlags;
 236         protected $mTrxLevel = 0;
 237         protected $mErrorCount = 0;
 238         protected $mLBInfo = array();
 239         protected $mFakeSlaveLag = null, $mFakeMaster = false;
 240         protected $mDefaultBigSelects = null;
 241         protected $mSchemaVars = false;
 242
 243         protected $preparedArgs;
 244
 245         protected $htmlErrors;
 246
 247         protected $delimiter = ';';
 248
 249 # ------------------------------------------------------------------------------
 250 # Accessors
 251 # ------------------------------------------------------------------------------
 252         # These optionally set a variable and return the previous state
 253
 254         /**
 255          * A string describing the current software version, and possibly
 256          * other details in a user-friendly way.  Will be listed on Special:Version, etc.
 257          * Use getServerVersion() to get machine-friendly information.
 258          *
 259          * @return string: Version information from the database server
 260          */
 261         public function getServerInfo() {
 262                 return $this->getServerVersion();
 263         }
 264
 265         /**
 266          * Boolean, controls output of large amounts of debug information.
 267          * @param $debug bool|null
 268          *   - true to enable debugging
 269          *   - false to disable debugging
 270          *   - omitted or null to do nothing
 271          *
 272          * @return bool|null previous value of the flag
 273          */
 274         public function debug( $debug = null ) {
 275                 return wfSetBit( $this->mFlags, DBO_DEBUG, $debug );
 276         }
 277
 278         /**
 279          * Turns buffering of SQL result sets on (true) or off (false). Default is
 280          * "on".
 281          *
 282          * Unbuffered queries are very troublesome in MySQL:
 283          *
 284          *   - If another query is executed while the first query is being read
 285          *     out, the first query is killed. This means you can't call normal
 286          *     MediaWiki functions while you are reading an unbuffered query result
 287          *     from a normal wfGetDB() connection.
 288          *
 289          *   - Unbuffered queries cause the MySQL server to use large amounts of
 290          *     memory and to hold broad locks which block other queries.
 291          *
 292          * If you want to limit client-side memory, it's almost always better to
 293          * split up queries into batches using a LIMIT clause than to switch off
 294          * buffering.
 295          *
 296          * @param $buffer null|bool
 297          *
 298          * @return null|bool The previous value of the flag
 299          */
 300         public function bufferResults( $buffer = null ) {
 301                 if ( is_null( $buffer ) ) {
 302                         return !(bool)( $this->mFlags & DBO_NOBUFFER );
 303                 } else {
 304                         return !wfSetBit( $this->mFlags, DBO_NOBUFFER, !$buffer );
 305                 }
 306         }
 307
 308         /**
 309          * Turns on (false) or off (true) the automatic generation and sending
 310          * of a "we're sorry, but there has been a database error" page on
 311          * database errors. Default is on (false). When turned off, the
 312          * code should use lastErrno() and lastError() to handle the
 313          * situation as appropriate.
 314          *
 315          * @param $ignoreErrors bool|null
 316          *
 317          * @return bool The previous value of the flag.
 318          */
 319         public function ignoreErrors( $ignoreErrors = null ) {
 320                 return wfSetBit( $this->mFlags, DBO_IGNORE, $ignoreErrors );
 321         }
 322
 323         /**
 324          * Gets or sets the current transaction level.
 325          *
 326          * Historically, transactions were allowed to be "nested". This is no
 327          * longer supported, so this function really only returns a boolean.
 328          *
 329          * @param $level int An integer (0 or 1), or omitted to leave it unchanged.
 330          * @return int The previous value
 331          */
 332         public function trxLevel( $level = null ) {
 333                 return wfSetVar( $this->mTrxLevel, $level );
 334         }
 335
 336         /**
 337          * Get/set the number of errors logged. Only useful when errors are ignored
 338          * @param $count int The count to set, or omitted to leave it unchanged.
 339          * @return int The error count
 340          */
 341         public function errorCount( $count = null ) {
 342                 return wfSetVar( $this->mErrorCount, $count );
 343         }
 344
 345         /**
 346          * Get/set the table prefix.
 347          * @param $prefix string The table prefix to set, or omitted to leave it unchanged.
 348          * @return string The previous table prefix.
 349          */
 350         public function tablePrefix( $prefix = null ) {
 351                 return wfSetVar( $this->mTablePrefix, $prefix );
 352         }
 353
 354         /**
 355          * Get properties passed down from the server info array of the load
 356          * balancer.
 357          *
 358          * @param $name string The entry of the info array to get, or null to get the
 359          *   whole array
 360          *
 361          * @return LoadBalancer|null
 362          */
 363         public function getLBInfo( $name = null ) {
 364                 if ( is_null( $name ) ) {
 365                         return $this->mLBInfo;
 366                 } else {
 367                         if ( array_key_exists( $name, $this->mLBInfo ) ) {
 368                                 return $this->mLBInfo[$name];
 369                         } else {
 370                                 return null;
 371                         }
 372                 }
 373         }
 374
 375         /**
 376          * Set the LB info array, or a member of it. If called with one parameter,
 377          * the LB info array is set to that parameter. If it is called with two
 378          * parameters, the member with the given name is set to the given value.
 379          *
 380          * @param $name
 381          * @param $value
 382          */
 383         public function setLBInfo( $name, $value = null ) {
 384                 if ( is_null( $value ) ) {
 385                         $this->mLBInfo = $name;
 386                 } else {
 387                         $this->mLBInfo[$name] = $value;
 388                 }
 389         }
 390
 391         /**
 392          * Set lag time in seconds for a fake slave
 393          *
 394          * @param $lag int
 395          */
 396         public function setFakeSlaveLag( $lag ) {
 397                 $this->mFakeSlaveLag = $lag;
 398         }
 399
 400         /**
 401          * Make this connection a fake master
 402          *
 403          * @param $enabled bool
 404          */
 405         public function setFakeMaster( $enabled = true ) {
 406                 $this->mFakeMaster = $enabled;
 407         }
 408
 409         /**
 410          * Returns true if this database supports (and uses) cascading deletes
 411          *
 412          * @return bool
 413          */
 414         public function cascadingDeletes() {
 415                 return false;
 416         }
 417
 418         /**
 419          * Returns true if this database supports (and uses) triggers (e.g. on the page table)
 420          *
 421          * @return bool
 422          */
 423         public function cleanupTriggers() {
 424                 return false;
 425         }
 426
 427         /**
 428          * Returns true if this database is strict about what can be put into an IP field.
 429          * Specifically, it uses a NULL value instead of an empty string.
 430          *
 431          * @return bool
 432          */
 433         public function strictIPs() {
 434                 return false;
 435         }
 436
 437         /**
 438          * Returns true if this database uses timestamps rather than integers
 439          *
 440          * @return bool
 441         */
 442         public function realTimestamps() {
 443                 return false;
 444         }
 445
 446         /**
 447          * Returns true if this database does an implicit sort when doing GROUP BY
 448          *
 449          * @return bool
 450          */
 451         public function implicitGroupby() {
 452                 return true;
 453         }
 454
 455         /**
 456          * Returns true if this database does an implicit order by when the column has an index
 457          * For example: SELECT page_title FROM page LIMIT 1
 458          *
 459          * @return bool
 460          */
 461         public function implicitOrderby() {
 462                 return true;
 463         }
 464
 465         /**
 466          * Returns true if this database can do a native search on IP columns
 467          * e.g. this works as expected: .. WHERE rc_ip = '127.42.12.102/32';
 468          *
 469          * @return bool
 470          */
 471         public function searchableIPs() {
 472                 return false;
 473         }
 474
 475         /**
 476          * Returns true if this database can use functional indexes
 477          *
 478          * @return bool
 479          */
 480         public function functionalIndexes() {
 481                 return false;
 482         }
 483
 484         /**
 485          * Return the last query that went through DatabaseBase::query()
 486          * @return String
 487          */
 488         public function lastQuery() {
 489                 return $this->mLastQuery;
 490         }
 491
 492         /**
 493          * Returns true if the connection may have been used for write queries.
 494          * Should return true if unsure.
 495          *
 496          * @return bool
 497          */
 498         public function doneWrites() {
 499                 return $this->mDoneWrites;
 500         }
 501
 502         /**
 503          * Is a connection to the database open?
 504          * @return Boolean
 505          */
 506         public function isOpen() {
 507                 return $this->mOpened;
 508         }
 509
 510         /**
 511          * Set a flag for this connection
 512          *
 513          * @param $flag Integer: DBO_* constants from Defines.php:
 514          *   - DBO_DEBUG: output some debug info (same as debug())
 515          *   - DBO_NOBUFFER: don't buffer results (inverse of bufferResults())
 516          *   - DBO_IGNORE: ignore errors (same as ignoreErrors())
 517          *   - DBO_TRX: automatically start transactions
 518          *   - DBO_DEFAULT: automatically sets DBO_TRX if not in command line mode
 519          *       and removes it in command line mode
 520          *   - DBO_PERSISTENT: use persistant database connection
 521          */
 522         public function setFlag( $flag ) {
 523                 global $wgDebugDBTransactions;
 524                 $this->mFlags |= $flag;
 525                 if ( ( $flag & DBO_TRX) & $wgDebugDBTransactions ) {
 526                         wfDebug("Implicit transactions are now  disabled.\n");
 527                 }
 528         }
 529
 530         /**
 531          * Clear a flag for this connection
 532          *
 533          * @param $flag: same as setFlag()'s $flag param
 534          */
 535         public function clearFlag( $flag ) {
 536                 global $wgDebugDBTransactions;
 537                 $this->mFlags &= ~$flag;
 538                 if ( ( $flag & DBO_TRX ) && $wgDebugDBTransactions ) {
 539                         wfDebug("Implicit transactions are now disabled.\n");
 540                 }
 541         }
 542
 543         /**
 544          * Returns a boolean whether the flag $flag is set for this connection
 545          *
 546          * @param $flag: same as setFlag()'s $flag param
 547          * @return Boolean
 548          */
 549         public function getFlag( $flag ) {
 550                 return !!( $this->mFlags & $flag );
 551         }
 552
 553         /**
 554          * General read-only accessor
 555          *
 556          * @param $name string
 557          *
 558          * @return string
 559          */
 560         public function getProperty( $name ) {
 561                 return $this->$name;
 562         }
 563
 564         /**
 565          * @return string
 566          */
 567         public function getWikiID() {
 568                 if ( $this->mTablePrefix ) {
 569                         return "{$this->mDBname}-{$this->mTablePrefix}";
 570                 } else {
 571                         return $this->mDBname;
 572                 }
 573         }
 574
 575         /**
 576          * Return a path to the DBMS-specific schema file, otherwise default to tables.sql
 577          *
 578          * @return string
 579          */
 580         public function getSchemaPath() {
 581                 global $IP;
 582                 if ( file_exists( "$IP/maintenance/" . $this->getType() . "/tables.sql" ) ) {
 583                         return "$IP/maintenance/" . $this->getType() . "/tables.sql";
 584                 } else {
 585                         return "$IP/maintenance/tables.sql";
 586                 }
 587         }
 588
 589 # ------------------------------------------------------------------------------
 590 # Other functions
 591 # ------------------------------------------------------------------------------
 592
 593         /**
 594          * Constructor.
 595          * @param $server String: database server host
 596          * @param $user String: database user name
 597          * @param $password String: database user password
 598          * @param $dbName String: database name
 599          * @param $flags
 600          * @param $tablePrefix String: database table prefixes. By default use the prefix gave in LocalSettings.php
 601          */
 602         function __construct( $server = false, $user = false, $password = false, $dbName = false,
 603                 $flags = 0, $tablePrefix = 'get from global'
 604         ) {
 605                 global $wgDBprefix, $wgCommandLineMode, $wgDebugDBTransactions;
 606
 607                 $this->mFlags = $flags;
 608
 609                 if ( $this->mFlags & DBO_DEFAULT ) {
 610                         if ( $wgCommandLineMode ) {
 611                                 $this->mFlags &= ~DBO_TRX;
 612                                 if ( $wgDebugDBTransactions ) {
 613                                         wfDebug("Implicit transaction open disabled.\n");
 614                                 }
 615                         } else {
 616                                 $this->mFlags |= DBO_TRX;
 617                                 if ( $wgDebugDBTransactions ) {
 618                                         wfDebug("Implicit transaction open enabled.\n");
 619                                 }
 620                         }
 621                 }
 622
 623                 /** Get the default table prefix*/
 624                 if ( $tablePrefix == 'get from global' ) {
 625                         $this->mTablePrefix = $wgDBprefix;
 626                 } else {
 627                         $this->mTablePrefix = $tablePrefix;
 628                 }
 629
 630                 if ( $user ) {
 631                         $this->open( $server, $user, $password, $dbName );
 632                 }
 633         }
 634
 635         /**
 636          * Called by serialize. Throw an exception when DB connection is serialized.
 637          * This causes problems on some database engines because the connection is
 638          * not restored on unserialize.
 639          */
 640         public function __sleep() {
 641                 throw new MWException( 'Database serialization may cause problems, since the connection is not restored on wakeup.' );
 642         }
 643
 644         /**
 645          * Given a DB type, construct the name of the appropriate child class of
 646          * DatabaseBase. This is designed to replace all of the manual stuff like:
 647          *      $class = 'Database' . ucfirst( strtolower( $type ) );
 648          * as well as validate against the canonical list of DB types we have
 649          *
 650          * This factory function is mostly useful for when you need to connect to a
 651          * database other than the MediaWiki default (such as for external auth,
 652          * an extension, et cetera). Do not use this to connect to the MediaWiki
 653          * database. Example uses in core:
 654          * @see LoadBalancer::reallyOpenConnection()
 655          * @see ExternalUser_MediaWiki::initFromCond()
 656          * @see ForeignDBRepo::getMasterDB()
 657          * @see WebInstaller_DBConnect::execute()
 658          *
 659          * @since 1.18
 660          *
 661          * @param $dbType String A possible DB type
 662          * @param $p Array An array of options to pass to the constructor.
 663          *    Valid options are: host, user, password, dbname, flags, tablePrefix
 664          * @return DatabaseBase subclass or null
 665          */
 666         public final static function factory( $dbType, $p = array() ) {
 667                 $canonicalDBTypes = array(
 668                         'mysql', 'postgres', 'sqlite', 'oracle', 'mssql', 'ibm_db2'
 669                 );
 670                 $dbType = strtolower( $dbType );
 671                 $class = 'Database' . ucfirst( $dbType );
 672
 673                 if( in_array( $dbType, $canonicalDBTypes ) || ( class_exists( $class ) && is_subclass_of( $class, 'DatabaseBase' ) ) ) {
 674                         return new $class(
 675                                 isset( $p['host'] ) ? $p['host'] : false,
 676                                 isset( $p['user'] ) ? $p['user'] : false,
 677                                 isset( $p['password'] ) ? $p['password'] : false,
 678                                 isset( $p['dbname'] ) ? $p['dbname'] : false,
 679                                 isset( $p['flags'] ) ? $p['flags'] : 0,
 680                                 isset( $p['tablePrefix'] ) ? $p['tablePrefix'] : 'get from global'
 681                         );
 682                 } else {
 683                         return null;
 684                 }
 685         }
 686
 687         protected function installErrorHandler() {
 688                 $this->mPHPError = false;
 689                 $this->htmlErrors = ini_set( 'html_errors', '0' );
 690                 set_error_handler( array( $this, 'connectionErrorHandler' ) );
 691         }
 692
 693         /**
 694          * @return bool|string
 695          */
 696         protected function restoreErrorHandler() {
 697                 restore_error_handler();
 698                 if ( $this->htmlErrors !== false ) {
 699                         ini_set( 'html_errors', $this->htmlErrors );
 700                 }
 701                 if ( $this->mPHPError ) {
 702                         $error = preg_replace( '!\[<a.*</a>\]!', '', $this->mPHPError );
 703                         $error = preg_replace( '!^.*?:\s?(.*)$!', '$1', $error );
 704                         return $error;
 705                 } else {
 706                         return false;
 707                 }
 708         }
 709
 710         /**
 711          * @param $errno
 712          * @param $errstr
 713          */
 714         protected function connectionErrorHandler( $errno,  $errstr ) {
 715                 $this->mPHPError = $errstr;
 716         }
 717
 718         /**
 719          * Closes a database connection.
 720          * if it is open : commits any open transactions
 721          *
 722          * @return Bool operation success. true if already closed.
 723          */
 724         public function close() {
 725                 $this->mOpened = false;
 726                 if ( $this->mConn ) {
 727                         if ( $this->trxLevel() ) {
 728                                 $this->commit( __METHOD__ );
 729                         }
 730                         $ret = $this->closeConnection();
 731                         $this->mConn = false;
 732                         return $ret;
 733                 } else {
 734                         return true;
 735                 }
 736         }
 737
 738         /**
 739          * Closes underlying database connection
 740          * @since 1.20
 741          * @return bool: Whether connection was closed successfully
 742          */
 743         protected abstract function closeConnection();
 744
 745         /**
 746          * @param $error String: fallback error message, used if none is given by DB
 747          */
 748         function reportConnectionError( $error = 'Unknown error' ) {
 749                 $myError = $this->lastError();
 750                 if ( $myError ) {
 751                         $error = $myError;
 752                 }
 753
 754                 # New method
 755                 throw new DBConnectionError( $this, $error );
 756         }
 757
 758         /**
 759          * The DBMS-dependent part of query()
 760          *
 761          * @param  $sql String: SQL query.
 762          * @return ResultWrapper Result object to feed to fetchObject, fetchRow, ...; or false on failure
 763          */
 764         protected abstract function doQuery( $sql );
 765
 766         /**
 767          * Determine whether a query writes to the DB.
 768          * Should return true if unsure.
 769          *
 770          * @param $sql string
 771          *
 772          * @return bool
 773          */
 774         public function isWriteQuery( $sql ) {
 775                 return !preg_match( '/^(?:SELECT|BEGIN|ROLLBACK|COMMIT|SET|SHOW|EXPLAIN|\(SELECT)\b/i', $sql );
 776         }
 777
 778         /**
 779          * Run an SQL query and return the result. Normally throws a DBQueryError
 780          * on failure. If errors are ignored, returns false instead.
 781          *
 782          * In new code, the query wrappers select(), insert(), update(), delete(),
 783          * etc. should be used where possible, since they give much better DBMS
 784          * independence and automatically quote or validate user input in a variety
 785          * of contexts. This function is generally only useful for queries which are
 786          * explicitly DBMS-dependent and are unsupported by the query wrappers, such
 787          * as CREATE TABLE.
 788          *
 789          * However, the query wrappers themselves should call this function.
 790          *
 791          * @param  $sql        String: SQL query
 792          * @param  $fname      String: Name of the calling function, for profiling/SHOW PROCESSLIST
 793          *     comment (you can use __METHOD__ or add some extra info)
 794          * @param  $tempIgnore Boolean:   Whether to avoid throwing an exception on errors...
 795          *     maybe best to catch the exception instead?
 796          * @return boolean|ResultWrapper. true for a successful write query, ResultWrapper object
 797          *     for a successful read query, or false on failure if $tempIgnore set
 798          * @throws DBQueryError Thrown when the database returns an error of any kind
 799          */
 800         public function query( $sql, $fname = '', $tempIgnore = false ) {
 801                 $isMaster = !is_null( $this->getLBInfo( 'master' ) );
 802                 if ( !Profiler::instance()->isStub() ) {
 803                         # generalizeSQL will probably cut down the query to reasonable
 804                         # logging size most of the time. The substr is really just a sanity check.
 805
 806                         if ( $isMaster ) {
 807                                 $queryProf = 'query-m: ' . substr( DatabaseBase::generalizeSQL( $sql ), 0, 255 );
 808                                 $totalProf = 'DatabaseBase::query-master';
 809                         } else {
 810                                 $queryProf = 'query: ' . substr( DatabaseBase::generalizeSQL( $sql ), 0, 255 );
 811                                 $totalProf = 'DatabaseBase::query';
 812                         }
 813
 814                         wfProfileIn( $totalProf );
 815                         wfProfileIn( $queryProf );
 816                 }
 817
 818                 $this->mLastQuery = $sql;
 819                 if ( !$this->mDoneWrites && $this->isWriteQuery( $sql ) ) {
 820                         # Set a flag indicating that writes have been done
 821                         wfDebug( __METHOD__ . ": Writes done: $sql\n" );
 822                         $this->mDoneWrites = true;
 823                 }
 824
 825                 # Add a comment for easy SHOW PROCESSLIST interpretation
 826                 global $wgUser;
 827                 if ( is_object( $wgUser ) && $wgUser->isItemLoaded( 'name' ) ) {
 828                         $userName = $wgUser->getName();
 829                         if ( mb_strlen( $userName ) > 15 ) {
 830                                 $userName = mb_substr( $userName, 0, 15 ) . '...';
 831                         }
 832                         $userName = str_replace( '/', '', $userName );
 833                 } else {
 834                         $userName = '';
 835                 }
 836                 $commentedSql = preg_replace( '/\s/', " /* $fname $userName */ ", $sql, 1 );
 837
 838                 # If DBO_TRX is set, start a transaction
 839                 if ( ( $this->mFlags & DBO_TRX ) && !$this->trxLevel() &&
 840                         $sql != 'BEGIN' && $sql != 'COMMIT' && $sql != 'ROLLBACK' ) {
 841                         # avoid establishing transactions for SHOW and SET statements too -
 842                         # that would delay transaction initializations to once connection
 843                         # is really used by application
 844                         $sqlstart = substr( $sql, 0, 10 ); // very much worth it, benchmark certified(tm)
 845                         if ( strpos( $sqlstart, "SHOW " ) !== 0 && strpos( $sqlstart, "SET " ) !== 0 ) {
 846                                 global $wgDebugDBTransactions;
 847                                 if ( $wgDebugDBTransactions ) {
 848                                         wfDebug("Implicit transaction start.\n");
 849                                 }
 850                                 $this->begin( __METHOD__ . " ($fname)" );
 851                         }
 852                 }
 853
 854                 if ( $this->debug() ) {
 855                         static $cnt = 0;
 856
 857                         $cnt++;
 858                         $sqlx = substr( $commentedSql, 0, 500 );
 859                         $sqlx = strtr( $sqlx, "\t\n", '  ' );
 860
 861                         $master = $isMaster ? 'master' : 'slave';
 862                         wfDebug( "Query {$this->mDBname} ($cnt) ($master): $sqlx\n" );
 863                 }
 864
 865                 if ( istainted( $sql ) & TC_MYSQL ) {
 866                         throw new MWException( 'Tainted query found' );
 867                 }
 868
 869                 $queryId = MWDebug::query( $sql, $fname, $isMaster );
 870
 871                 # Do the query and handle errors
 872                 $ret = $this->doQuery( $commentedSql );
 873
 874                 MWDebug::queryTime( $queryId );
 875
 876                 # Try reconnecting if the connection was lost
 877                 if ( false === $ret && $this->wasErrorReissuable() ) {
 878                         # Transaction is gone, like it or not
 879                         $this->mTrxLevel = 0;
 880                         wfDebug( "Connection lost, reconnecting...\n" );
 881
 882                         if ( $this->ping() ) {
 883                                 wfDebug( "Reconnected\n" );
 884                                 $sqlx = substr( $commentedSql, 0, 500 );
 885                                 $sqlx = strtr( $sqlx, "\t\n", '  ' );
 886                                 global $wgRequestTime;
 887                                 $elapsed = round( microtime( true ) - $wgRequestTime, 3 );
 888                                 if ( $elapsed < 300 ) {
 889                                         # Not a database error to lose a transaction after a minute or two
 890                                         wfLogDBError( "Connection lost and reconnected after {$elapsed}s, query: $sqlx\n" );
 891                                 }
 892                                 $ret = $this->doQuery( $commentedSql );
 893                         } else {
 894                                 wfDebug( "Failed\n" );
 895                         }
 896                 }
 897
 898                 if ( false === $ret ) {
 899                         $this->reportQueryError( $this->lastError(), $this->lastErrno(), $sql, $fname, $tempIgnore );
 900                 }
 901
 902                 if ( !Profiler::instance()->isStub() ) {
 903                         wfProfileOut( $queryProf );
 904                         wfProfileOut( $totalProf );
 905                 }
 906
 907                 return $this->resultObject( $ret );
 908         }
 909
 910         /**
 911          * Report a query error. Log the error, and if neither the object ignore
 912          * flag nor the $tempIgnore flag is set, throw a DBQueryError.
 913          *
 914          * @param $error String
 915          * @param $errno Integer
 916          * @param $sql String
 917          * @param $fname String
 918          * @param $tempIgnore Boolean
 919          */
 920         public function reportQueryError( $error, $errno, $sql, $fname, $tempIgnore = false ) {
 921                 # Ignore errors during error handling to avoid infinite recursion
 922                 $ignore = $this->ignoreErrors( true );
 923                 ++$this->mErrorCount;
 924
 925                 if ( $ignore || $tempIgnore ) {
 926                         wfDebug( "SQL ERROR (ignored): $error\n" );
 927                         $this->ignoreErrors( $ignore );
 928                 } else {
 929                         $sql1line = str_replace( "\n", "\\n", $sql );
 930                         wfLogDBError( "$fname\t{$this->mServer}\t$errno\t$error\t$sql1line\n" );
 931                         wfDebug( "SQL ERROR: " . $error . "\n" );
 932                         throw new DBQueryError( $this, $error, $errno, $sql, $fname );
 933                 }
 934         }
 935
 936         /**
 937          * Intended to be compatible with the PEAR::DB wrapper functions.
 938          * http://pear.php.net/manual/en/package.database.db.intro-execute.php
 939          *
 940          * ? = scalar value, quoted as necessary
 941          * ! = raw SQL bit (a function for instance)
 942          * & = filename; reads the file and inserts as a blob
 943          *     (we don't use this though...)
 944          *
 945          * @param $sql string
 946          * @param $func string
 947          *
 948          * @return array
 949          */
 950         protected function prepare( $sql, $func = 'DatabaseBase::prepare' ) {
 951                 /* MySQL doesn't support prepared statements (yet), so just
 952                    pack up the query for reference. We'll manually replace
 953                    the bits later. */
 954                 return array( 'query' => $sql, 'func' => $func );
 955         }
 956
 957         /**
 958          * Free a prepared query, generated by prepare().
 959          * @param $prepared
 960          */
 961         protected function freePrepared( $prepared ) {
 962                 /* No-op by default */
 963         }
 964
 965         /**
 966          * Execute a prepared query with the various arguments
 967          * @param $prepared String: the prepared sql
 968          * @param $args Mixed: Either an array here, or put scalars as varargs
 969          *
 970          * @return ResultWrapper
 971          */
 972         public function execute( $prepared, $args = null ) {
 973                 if ( !is_array( $args ) ) {
 974                         # Pull the var args
 975                         $args = func_get_args();
 976                         array_shift( $args );
 977                 }
 978
 979                 $sql = $this->fillPrepared( $prepared['query'], $args );
 980
 981                 return $this->query( $sql, $prepared['func'] );
 982         }
 983
 984         /**
 985          * For faking prepared SQL statements on DBs that don't support it directly.
 986          *
 987          * @param $preparedQuery String: a 'preparable' SQL statement
 988          * @param $args Array of arguments to fill it with
 989          * @return string executable SQL
 990          */
 991         public function fillPrepared( $preparedQuery, $args ) {
 992                 reset( $args );
 993                 $this->preparedArgs =& $args;
 994
 995                 return preg_replace_callback( '/(\\\\[?!&]|[?!&])/',
 996                         array( &$this, 'fillPreparedArg' ), $preparedQuery );
 997         }
 998
 999         /**
1000          * preg_callback func for fillPrepared()
1001          * The arguments should be in $this->preparedArgs and must not be touched
1002          * while we're doing this.
1003          *
1004          * @param $matches Array
1005          * @return String
1006          */
1007         protected function fillPreparedArg( $matches ) {
1008                 switch( $matches[1] ) {
1009                         case '\\?': return '?';
1010                         case '\\!': return '!';
1011                         case '\\&': return '&';
1012                 }
1013
1014                 list( /* $n */ , $arg ) = each( $this->preparedArgs );
1015
1016                 switch( $matches[1] ) {
1017                         case '?': return $this->addQuotes( $arg );
1018                         case '!': return $arg;
1019                         case '&':
1020                                 # return $this->addQuotes( file_get_contents( $arg ) );
1021                                 throw new DBUnexpectedError( $this, '& mode is not implemented. If it\'s really needed, uncomment the line above.' );
1022                         default:
1023                                 throw new DBUnexpectedError( $this, 'Received invalid match. This should never happen!' );
1024                 }
1025         }
1026
1027         /**
1028          * Free a result object returned by query() or select(). It's usually not
1029          * necessary to call this, just use unset() or let the variable holding
1030          * the result object go out of scope.
1031          *
1032          * @param $res Mixed: A SQL result
1033          */
1034         public function freeResult( $res ) {}
1035
1036         /**
1037          * A SELECT wrapper which returns a single field from a single result row.
1038          *
1039          * Usually throws a DBQueryError on failure. If errors are explicitly
1040          * ignored, returns false on failure.
1041          *
1042          * If no result rows are returned from the query, false is returned.
1043          *
1044          * @param $table string|array Table name. See DatabaseBase::select() for details.
1045          * @param $var string The field name to select. This must be a valid SQL
1046          *   fragment: do not use unvalidated user input.
1047          * @param $cond string|array The condition array. See DatabaseBase::select() for details.
1048          * @param $fname string The function name of the caller.
1049          * @param $options string|array The query options. See DatabaseBase::select() for details.
1050          *
1051          * @return bool|mixed The value from the field, or false on failure.
1052          */
1053         public function selectField( $table, $var, $cond = '', $fname = 'DatabaseBase::selectField',
1054                 $options = array() )
1055         {
1056                 if ( !is_array( $options ) ) {
1057                         $options = array( $options );
1058                 }
1059
1060                 $options['LIMIT'] = 1;
1061
1062                 $res = $this->select( $table, $var, $cond, $fname, $options );
1063
1064                 if ( $res === false || !$this->numRows( $res ) ) {
1065                         return false;
1066                 }
1067
1068                 $row = $this->fetchRow( $res );
1069
1070                 if ( $row !== false ) {
1071                         return reset( $row );
1072                 } else {
1073                         return false;
1074                 }
1075         }
1076
1077         /**
1078          * Returns an optional USE INDEX clause to go after the table, and a
1079          * string to go at the end of the query.
1080          *
1081          * @param $options Array: associative array of options to be turned into
1082          *              an SQL query, valid keys are listed in the function.
1083          * @return Array
1084          * @see DatabaseBase::select()
1085          */
1086         public function makeSelectOptions( $options ) {
1087                 $preLimitTail = $postLimitTail = '';
1088                 $startOpts = '';
1089
1090                 $noKeyOptions = array();
1091
1092                 foreach ( $options as $key => $option ) {
1093                         if ( is_numeric( $key ) ) {
1094                                 $noKeyOptions[$option] = true;
1095                         }
1096                 }
1097
1098                 if ( isset( $options['GROUP BY'] ) ) {
1099                         $gb = is_array( $options['GROUP BY'] )
1100                                 ? implode( ',', $options['GROUP BY'] )
1101                                 : $options['GROUP BY'];
1102                         $preLimitTail .= " GROUP BY {$gb}";
1103                 }
1104
1105                 if ( isset( $options['HAVING'] ) ) {
1106                         $having = is_array( $options['HAVING'] )
1107                                 ? $this->makeList( $options['HAVING'], LIST_AND )
1108                                 : $options['HAVING'];
1109                         $preLimitTail .= " HAVING {$having}";
1110                 }
1111
1112                 if ( isset( $options['ORDER BY'] ) ) {
1113                         $ob = is_array( $options['ORDER BY'] )
1114                                 ? implode( ',', $options['ORDER BY'] )
1115                                 : $options['ORDER BY'];
1116                         $preLimitTail .= " ORDER BY {$ob}";
1117                 }
1118
1119                 // if (isset($options['LIMIT'])) {
1120                 //      $tailOpts .= $this->limitResult('', $options['LIMIT'],
1121                 //              isset($options['OFFSET']) ? $options['OFFSET']
1122                 //              : false);
1123                 // }
1124
1125                 if ( isset( $noKeyOptions['FOR UPDATE'] ) ) {
1126                         $postLimitTail .= ' FOR UPDATE';
1127                 }
1128
1129                 if ( isset( $noKeyOptions['LOCK IN SHARE MODE'] ) ) {
1130                         $postLimitTail .= ' LOCK IN SHARE MODE';
1131                 }
1132
1133                 if ( isset( $noKeyOptions['DISTINCT'] ) || isset( $noKeyOptions['DISTINCTROW'] ) ) {
1134                         $startOpts .= 'DISTINCT';
1135                 }
1136
1137                 # Various MySQL extensions
1138                 if ( isset( $noKeyOptions['STRAIGHT_JOIN'] ) ) {
1139                         $startOpts .= ' /*! STRAIGHT_JOIN */';
1140                 }
1141
1142                 if ( isset( $noKeyOptions['HIGH_PRIORITY'] ) ) {
1143                         $startOpts .= ' HIGH_PRIORITY';
1144                 }
1145
1146                 if ( isset( $noKeyOptions['SQL_BIG_RESULT'] ) ) {
1147                         $startOpts .= ' SQL_BIG_RESULT';
1148                 }
1149
1150                 if ( isset( $noKeyOptions['SQL_BUFFER_RESULT'] ) ) {
1151                         $startOpts .= ' SQL_BUFFER_RESULT';
1152                 }
1153
1154                 if ( isset( $noKeyOptions['SQL_SMALL_RESULT'] ) ) {
1155                         $startOpts .= ' SQL_SMALL_RESULT';
1156                 }
1157
1158                 if ( isset( $noKeyOptions['SQL_CALC_FOUND_ROWS'] ) ) {
1159                         $startOpts .= ' SQL_CALC_FOUND_ROWS';
1160                 }
1161
1162                 if ( isset( $noKeyOptions['SQL_CACHE'] ) ) {
1163                         $startOpts .= ' SQL_CACHE';
1164                 }
1165
1166                 if ( isset( $noKeyOptions['SQL_NO_CACHE'] ) ) {
1167                         $startOpts .= ' SQL_NO_CACHE';
1168                 }
1169
1170                 if ( isset( $options['USE INDEX'] ) && ! is_array( $options['USE INDEX'] ) ) {
1171                         $useIndex = $this->useIndexClause( $options['USE INDEX'] );
1172                 } else {
1173                         $useIndex = '';
1174                 }
1175
1176                 return array( $startOpts, $useIndex, $preLimitTail, $postLimitTail );
1177         }
1178
1179         /**
1180          * Execute a SELECT query constructed using the various parameters provided.
1181          * See below for full details of the parameters.
1182          *
1183          * @param $table String|Array Table name
1184          * @param $vars String|Array Field names
1185          * @param $conds String|Array Conditions
1186          * @param $fname String Caller function name
1187          * @param $options Array Query options
1188          * @param $join_conds Array Join conditions
1189          *
1190          * @param $table string|array
1191          *
1192          * May be either an array of table names, or a single string holding a table
1193          * name. If an array is given, table aliases can be specified, for example:
1194          *
1195          *    array( 'a' => 'user' )
1196          *
1197          * This includes the user table in the query, with the alias "a" available
1198          * for use in field names (e.g. a.user_name).
1199          *
1200          * All of the table names given here are automatically run through
1201          * DatabaseBase::tableName(), which causes the table prefix (if any) to be
1202          * added, and various other table name mappings to be performed.
1203          *
1204          *
1205          * @param $vars string|array
1206          *
1207          * May be either a field name or an array of field names. The field names
1208          * can be complete fragments of SQL, for direct inclusion into the SELECT
1209          * query. If an array is given, field aliases can be specified, for example:
1210          *
1211          *   array( 'maxrev' => 'MAX(rev_id)' )
1212          *
1213          * This includes an expression with the alias "maxrev" in the query.
1214          *
1215          * If an expression is given, care must be taken to ensure that it is
1216          * DBMS-independent.
1217          *
1218          *
1219          * @param $conds string|array
1220          *
1221          * May be either a string containing a single condition, or an array of
1222          * conditions. If an array is given, the conditions constructed from each
1223          * element are combined with AND.
1224          *
1225          * Array elements may take one of two forms:
1226          *
1227          *   - Elements with a numeric key are interpreted as raw SQL fragments.
1228          *   - Elements with a string key are interpreted as equality conditions,
1229          *     where the key is the field name.
1230          *     - If the value of such an array element is a scalar (such as a
1231          *       string), it will be treated as data and thus quoted appropriately.
1232          *       If it is null, an IS NULL clause will be added.
1233          *     - If the value is an array, an IN(...) clause will be constructed,
1234          *       such that the field name may match any of the elements in the
1235          *       array. The elements of the array will be quoted.
1236          *
1237          * Note that expressions are often DBMS-dependent in their syntax.
1238          * DBMS-independent wrappers are provided for constructing several types of
1239          * expression commonly used in condition queries. See:
1240          *    - DatabaseBase::buildLike()
1241          *    - DatabaseBase::conditional()
1242          *
1243          *
1244          * @param $options string|array
1245          *
1246          * Optional: Array of query options. Boolean options are specified by
1247          * including them in the array as a string value with a numeric key, for
1248          * example:
1249          *
1250          *    array( 'FOR UPDATE' )
1251          *
1252          * The supported options are:
1253          *
1254          *   - OFFSET: Skip this many rows at the start of the result set. OFFSET
1255          *     with LIMIT can theoretically be used for paging through a result set,
1256          *     but this is discouraged in MediaWiki for performance reasons.
1257          *
1258          *   - LIMIT: Integer: return at most this many rows. The rows are sorted
1259          *     and then the first rows are taken until the limit is reached. LIMIT
1260          *     is applied to a result set after OFFSET.
1261          *
1262          *   - FOR UPDATE: Boolean: lock the returned rows so that they can't be
1263          *     changed until the next COMMIT.
1264          *
1265          *   - DISTINCT: Boolean: return only unique result rows.
1266          *
1267          *   - GROUP BY: May be either an SQL fragment string naming a field or
1268          *     expression to group by, or an array of such SQL fragments.
1269          *
1270          *   - HAVING: May be either an string containing a HAVING clause or an array of
1271          *     conditions building the HAVING clause. If an array is given, the conditions
1272          *     constructed from each element are combined with AND.
1273          *
1274          *   - ORDER BY: May be either an SQL fragment giving a field name or
1275          *     expression to order by, or an array of such SQL fragments.
1276          *
1277          *   - USE INDEX: This may be either a string giving the index name to use
1278          *     for the query, or an array. If it is an associative array, each key
1279          *     gives the table name (or alias), each value gives the index name to
1280          *     use for that table. All strings are SQL fragments and so should be
1281          *     validated by the caller.
1282          *
1283          *   - EXPLAIN: In MySQL, this causes an EXPLAIN SELECT query to be run,
1284          *     instead of SELECT.
1285          *
1286          * And also the following boolean MySQL extensions, see the MySQL manual
1287          * for documentation:
1288          *
1289          *    - LOCK IN SHARE MODE
1290          *    - STRAIGHT_JOIN
1291          *    - HIGH_PRIORITY
1292          *    - SQL_BIG_RESULT
1293          *    - SQL_BUFFER_RESULT
1294          *    - SQL_SMALL_RESULT
1295          *    - SQL_CALC_FOUND_ROWS
1296          *    - SQL_CACHE
1297          *    - SQL_NO_CACHE
1298          *
1299          *
1300          * @param $join_conds string|array
1301          *
1302          * Optional associative array of table-specific join conditions. In the
1303          * most common case, this is unnecessary, since the join condition can be
1304          * in $conds. However, it is useful for doing a LEFT JOIN.
1305          *
1306          * The key of the array contains the table name or alias. The value is an
1307          * array with two elements, numbered 0 and 1. The first gives the type of
1308          * join, the second is an SQL fragment giving the join condition for that
1309          * table. For example:
1310          *
1311          *    array( 'page' => array('LEFT JOIN','page_latest=rev_id') )
1312          *
1313          * @return ResultWrapper. If the query returned no rows, a ResultWrapper
1314          *   with no rows in it will be returned. If there was a query error, a
1315          *   DBQueryError exception will be thrown, except if the "ignore errors"
1316          *   option was set, in which case false will be returned.
1317          */
1318         public function select( $table, $vars, $conds = '', $fname = 'DatabaseBase::select',
1319                 $options = array(), $join_conds = array() ) {
1320                 $sql = $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
1321
1322                 return $this->query( $sql, $fname );
1323         }
1324
1325         /**
1326          * The equivalent of DatabaseBase::select() except that the constructed SQL
1327          * is returned, instead of being immediately executed. This can be useful for
1328          * doing UNION queries, where the SQL text of each query is needed. In general,
1329          * however, callers outside of Database classes should just use select().
1330          *
1331          * @param $table string|array Table name
1332          * @param $vars string|array Field names
1333          * @param $conds string|array Conditions
1334          * @param $fname string Caller function name
1335          * @param $options string|array Query options
1336          * @param $join_conds string|array Join conditions
1337          *
1338          * @return string SQL query string.
1339          * @see DatabaseBase::select()
1340          */
1341         public function selectSQLText( $table, $vars, $conds = '', $fname = 'DatabaseBase::select',
1342                 $options = array(), $join_conds = array() )
1343         {
1344                 if ( is_array( $vars ) ) {
1345                         $vars = implode( ',', $this->fieldNamesWithAlias( $vars ) );
1346                 }
1347
1348                 $options = (array)$options;
1349
1350                 if ( is_array( $table ) ) {
1351                         $useIndex = ( isset( $options['USE INDEX'] ) && is_array( $options['USE INDEX'] ) )
1352                                 ? $options['USE INDEX']
1353                                 : array();
1354                         if ( count( $join_conds ) || count( $useIndex ) ) {
1355                                 $from = ' FROM ' .
1356                                         $this->tableNamesWithUseIndexOrJOIN( $table, $useIndex, $join_conds );
1357                         } else {
1358                                 $from = ' FROM ' . implode( ',', $this->tableNamesWithAlias( $table ) );
1359                         }
1360                 } elseif ( $table != '' ) {
1361                         if ( $table[0] == ' ' ) {
1362                                 $from = ' FROM ' . $table;
1363                         } else {
1364                                 $from = ' FROM ' . $this->tableName( $table );
1365                         }
1366                 } else {
1367                         $from = '';
1368                 }
1369
1370                 list( $startOpts, $useIndex, $preLimitTail, $postLimitTail ) = $this->makeSelectOptions( $options );
1371
1372                 if ( !empty( $conds ) ) {
1373                         if ( is_array( $conds ) ) {
1374                                 $conds = $this->makeList( $conds, LIST_AND );
1375                         }
1376                         $sql = "SELECT $startOpts $vars $from $useIndex WHERE $conds $preLimitTail";
1377                 } else {
1378                         $sql = "SELECT $startOpts $vars $from $useIndex $preLimitTail";
1379                 }
1380
1381                 if ( isset( $options['LIMIT'] ) ) {
1382                         $sql = $this->limitResult( $sql, $options['LIMIT'],
1383                                 isset( $options['OFFSET'] ) ? $options['OFFSET'] : false );
1384                 }
1385                 $sql = "$sql $postLimitTail";
1386
1387                 if ( isset( $options['EXPLAIN'] ) ) {
1388                         $sql = 'EXPLAIN ' . $sql;
1389                 }
1390
1391                 return $sql;
1392         }
1393
1394         /**
1395          * Single row SELECT wrapper. Equivalent to DatabaseBase::select(), except
1396          * that a single row object is returned. If the query returns no rows,
1397          * false is returned.
1398          *
1399          * @param $table string|array Table name
1400          * @param $vars string|array Field names
1401          * @param $conds array Conditions
1402          * @param $fname string Caller function name
1403          * @param $options string|array Query options
1404          * @param $join_conds array|string Join conditions
1405          *
1406          * @return object|bool
1407          */
1408         public function selectRow( $table, $vars, $conds, $fname = 'DatabaseBase::selectRow',
1409                 $options = array(), $join_conds = array() )
1410         {
1411                 $options = (array)$options;
1412                 $options['LIMIT'] = 1;
1413                 $res = $this->select( $table, $vars, $conds, $fname, $options, $join_conds );
1414
1415                 if ( $res === false ) {
1416                         return false;
1417                 }
1418
1419                 if ( !$this->numRows( $res ) ) {
1420                         return false;
1421                 }
1422
1423                 $obj = $this->fetchObject( $res );
1424
1425                 return $obj;
1426         }
1427
1428         /**
1429          * Estimate rows in dataset.
1430          *
1431          * MySQL allows you to estimate the number of rows that would be returned
1432          * by a SELECT query, using EXPLAIN SELECT. The estimate is provided using
1433          * index cardinality statistics, and is notoriously inaccurate, especially
1434          * when large numbers of rows have recently been added or deleted.
1435          *
1436          * For DBMSs that don't support fast result size estimation, this function
1437          * will actually perform the SELECT COUNT(*).
1438          *
1439          * Takes the same arguments as DatabaseBase::select().
1440          *
1441          * @param $table String: table name
1442          * @param Array|string $vars : unused
1443          * @param Array|string $conds : filters on the table
1444          * @param $fname String: function name for profiling
1445          * @param $options Array: options for select
1446          * @return Integer: row count
1447          */
1448         public function estimateRowCount( $table, $vars = '*', $conds = '',
1449                 $fname = 'DatabaseBase::estimateRowCount', $options = array() )
1450         {
1451                 $rows = 0;
1452                 $res = $this->select( $table, array( 'rowcount' => 'COUNT(*)' ), $conds, $fname, $options );
1453
1454                 if ( $res ) {
1455                         $row = $this->fetchRow( $res );
1456                         $rows = ( isset( $row['rowcount'] ) ) ? $row['rowcount'] : 0;
1457                 }
1458
1459                 return $rows;
1460         }
1461
1462         /**
1463          * Removes most variables from an SQL query and replaces them with X or N for numbers.
1464          * It's only slightly flawed. Don't use for anything important.
1465          *
1466          * @param $sql String A SQL Query
1467          *
1468          * @return string
1469          */
1470         static function generalizeSQL( $sql ) {
1471                 # This does the same as the regexp below would do, but in such a way
1472                 # as to avoid crashing php on some large strings.
1473                 # $sql = preg_replace ( "/'([^\\\\']|\\\\.)*'|\"([^\\\\\"]|\\\\.)*\"/", "'X'", $sql);
1474
1475                 $sql = str_replace ( "\\\\", '', $sql );
1476                 $sql = str_replace ( "\\'", '', $sql );
1477                 $sql = str_replace ( "\\\"", '', $sql );
1478                 $sql = preg_replace ( "/'.*'/s", "'X'", $sql );
1479                 $sql = preg_replace ( '/".*"/s', "'X'", $sql );
1480
1481                 # All newlines, tabs, etc replaced by single space
1482                 $sql = preg_replace ( '/\s+/', ' ', $sql );
1483
1484                 # All numbers => N
1485                 $sql = preg_replace ( '/-?[0-9]+/s', 'N', $sql );
1486
1487                 return $sql;
1488         }
1489
1490         /**
1491          * Determines whether a field exists in a table
1492          *
1493          * @param $table String: table name
1494          * @param $field String: filed to check on that table
1495          * @param $fname String: calling function name (optional)
1496          * @return Boolean: whether $table has filed $field
1497          */
1498         public function fieldExists( $table, $field, $fname = 'DatabaseBase::fieldExists' ) {
1499                 $info = $this->fieldInfo( $table, $field );
1500
1501                 return (bool)$info;
1502         }
1503
1504         /**
1505          * Determines whether an index exists
1506          * Usually throws a DBQueryError on failure
1507          * If errors are explicitly ignored, returns NULL on failure
1508          *
1509          * @param $table
1510          * @param $index
1511          * @param $fname string
1512          *
1513          * @return bool|null
1514          */
1515         public function indexExists( $table, $index, $fname = 'DatabaseBase::indexExists' ) {
1516                 $info = $this->indexInfo( $table, $index, $fname );
1517                 if ( is_null( $info ) ) {
1518                         return null;
1519                 } else {
1520                         return $info !== false;
1521                 }
1522         }
1523
1524         /**
1525          * Query whether a given table exists
1526          *
1527          * @param $table string
1528          * @param $fname string
1529          *
1530          * @return bool
1531          */
1532         public function tableExists( $table, $fname = __METHOD__ ) {
1533                 $table = $this->tableName( $table );
1534                 $old = $this->ignoreErrors( true );
1535                 $res = $this->query( "SELECT 1 FROM $table LIMIT 1", $fname );
1536                 $this->ignoreErrors( $old );
1537
1538                 return (bool)$res;
1539         }
1540
1541         /**
1542          * mysql_field_type() wrapper
1543          * @param $res
1544          * @param $index
1545          * @return string
1546          */
1547         public function fieldType( $res, $index ) {
1548                 if ( $res instanceof ResultWrapper ) {
1549                         $res = $res->result;
1550                 }
1551
1552                 return mysql_field_type( $res, $index );
1553         }
1554
1555         /**
1556          * Determines if a given index is unique
1557          *
1558          * @param $table string
1559          * @param $index string
1560          *
1561          * @return bool
1562          */
1563         public function indexUnique( $table, $index ) {
1564                 $indexInfo = $this->indexInfo( $table, $index );
1565
1566                 if ( !$indexInfo ) {
1567                         return null;
1568                 }
1569
1570                 return !$indexInfo[0]->Non_unique;
1571         }
1572
1573         /**
1574          * Helper for DatabaseBase::insert().
1575          *
1576          * @param $options array
1577          * @return string
1578          */
1579         protected function makeInsertOptions( $options ) {
1580                 return implode( ' ', $options );
1581         }
1582
1583         /**
1584          * INSERT wrapper, inserts an array into a table.
1585          *
1586          * $a may be either:
1587          *
1588          *   - A single associative array. The array keys are the field names, and
1589          *     the values are the values to insert. The values are treated as data
1590          *     and will be quoted appropriately. If NULL is inserted, this will be
1591          *     converted to a database NULL.
1592          *   - An array with numeric keys, holding a list of associative arrays.
1593          *     This causes a multi-row INSERT on DBMSs that support it. The keys in
1594          *     each subarray must be identical to each other, and in the same order.
1595          *
1596          * Usually throws a DBQueryError on failure. If errors are explicitly ignored,
1597          * returns success.
1598          *
1599          * $options is an array of options, with boolean options encoded as values
1600          * with numeric keys, in the same style as $options in
1601          * DatabaseBase::select(). Supported options are:
1602          *
1603          *   - IGNORE: Boolean: if present, duplicate key errors are ignored, and
1604          *     any rows which cause duplicate key errors are not inserted. It's
1605          *     possible to determine how many rows were successfully inserted using
1606          *     DatabaseBase::affectedRows().
1607          *
1608          * @param $table   String Table name. This will be passed through
1609          *                 DatabaseBase::tableName().
1610          * @param $a       Array of rows to insert
1611          * @param $fname   String Calling function name (use __METHOD__) for logs/profiling
1612          * @param $options Array of options
1613          *
1614          * @return bool
1615          */
1616         public function insert( $table, $a, $fname = 'DatabaseBase::insert', $options = array() ) {
1617                 # No rows to insert, easy just return now
1618                 if ( !count( $a ) ) {
1619                         return true;
1620                 }
1621
1622                 $table = $this->tableName( $table );
1623
1624                 if ( !is_array( $options ) ) {
1625                         $options = array( $options );
1626                 }
1627
1628                 $options = $this->makeInsertOptions( $options );
1629
1630                 if ( isset( $a[0] ) && is_array( $a[0] ) ) {
1631                         $multi = true;
1632                         $keys = array_keys( $a[0] );
1633                 } else {
1634                         $multi = false;
1635                         $keys = array_keys( $a );
1636                 }
1637
1638                 $sql = 'INSERT ' . $options .
1639                         " INTO $table (" . implode( ',', $keys ) . ') VALUES ';
1640
1641                 if ( $multi ) {
1642                         $first = true;
1643                         foreach ( $a as $row ) {
1644                                 if ( $first ) {
1645                                         $first = false;
1646                                 } else {
1647                                         $sql .= ',';
1648                                 }
1649                                 $sql .= '(' . $this->makeList( $row ) . ')';
1650                         }
1651                 } else {
1652                         $sql .= '(' . $this->makeList( $a ) . ')';
1653                 }
1654
1655                 return (bool)$this->query( $sql, $fname );
1656         }
1657
1658         /**
1659          * Make UPDATE options for the DatabaseBase::update function
1660          *
1661          * @param $options Array: The options passed to DatabaseBase::update
1662          * @return string
1663          */
1664         protected function makeUpdateOptions( $options ) {
1665                 if ( !is_array( $options ) ) {
1666                         $options = array( $options );
1667                 }
1668
1669                 $opts = array();
1670
1671                 if ( in_array( 'LOW_PRIORITY', $options ) ) {
1672                         $opts[] = $this->lowPriorityOption();
1673                 }
1674
1675                 if ( in_array( 'IGNORE', $options ) ) {
1676                         $opts[] = 'IGNORE';
1677                 }
1678
1679                 return implode( ' ', $opts );
1680         }
1681
1682         /**
1683          * UPDATE wrapper. Takes a condition array and a SET array.
1684          *
1685          * @param $table  String name of the table to UPDATE. This will be passed through
1686          *                DatabaseBase::tableName().
1687          *
1688          * @param $values Array:  An array of values to SET. For each array element,
1689          *                the key gives the field name, and the value gives the data
1690          *                to set that field to. The data will be quoted by
1691          *                DatabaseBase::addQuotes().
1692          *
1693          * @param $conds  Array:  An array of conditions (WHERE). See
1694          *                DatabaseBase::select() for the details of the format of
1695          *                condition arrays. Use '*' to update all rows.
1696          *
1697          * @param $fname  String: The function name of the caller (from __METHOD__),
1698          *                for logging and profiling.
1699          *
1700          * @param $options Array: An array of UPDATE options, can be:
1701          *                   - IGNORE: Ignore unique key conflicts
1702          *                   - LOW_PRIORITY: MySQL-specific, see MySQL manual.
1703          * @return Boolean
1704          */
1705         function update( $table, $values, $conds, $fname = 'DatabaseBase::update', $options = array() ) {
1706                 $table = $this->tableName( $table );
1707                 $opts = $this->makeUpdateOptions( $options );
1708                 $sql = "UPDATE $opts $table SET " . $this->makeList( $values, LIST_SET );
1709
1710                 if ( $conds !== array() && $conds !== '*' ) {
1711                         $sql .= " WHERE " . $this->makeList( $conds, LIST_AND );
1712                 }
1713
1714                 return $this->query( $sql, $fname );
1715         }
1716
1717         /**
1718          * Makes an encoded list of strings from an array
1719          * @param $a Array containing the data
1720          * @param $mode int Constant
1721          *      - LIST_COMMA:          comma separated, no field names
1722          *      - LIST_AND:            ANDed WHERE clause (without the WHERE). See
1723          *        the documentation for $conds in DatabaseBase::select().
1724          *      - LIST_OR:             ORed WHERE clause (without the WHERE)
1725          *      - LIST_SET:            comma separated with field names, like a SET clause
1726          *      - LIST_NAMES:          comma separated field names
1727          *
1728          * @return string
1729          */
1730         public function makeList( $a, $mode = LIST_COMMA ) {
1731                 if ( !is_array( $a ) ) {
1732                         throw new DBUnexpectedError( $this, 'DatabaseBase::makeList called with incorrect parameters' );
1733                 }
1734
1735                 $first = true;
1736                 $list = '';
1737
1738                 foreach ( $a as $field => $value ) {
1739                         if ( !$first ) {
1740                                 if ( $mode == LIST_AND ) {
1741                                         $list .= ' AND ';
1742                                 } elseif ( $mode == LIST_OR ) {
1743                                         $list .= ' OR ';
1744                                 } else {
1745                                         $list .= ',';
1746                                 }
1747                         } else {
1748                                 $first = false;
1749                         }
1750
1751                         if ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_numeric( $field ) ) {
1752                                 $list .= "($value)";
1753                         } elseif ( ( $mode == LIST_SET ) && is_numeric( $field ) ) {
1754                                 $list .= "$value";
1755                         } elseif ( ( $mode == LIST_AND || $mode == LIST_OR ) && is_array( $value ) ) {
1756                                 if ( count( $value ) == 0 ) {
1757                                         throw new MWException( __METHOD__ . ': empty input' );
1758                                 } elseif ( count( $value ) == 1 ) {
1759                                         // Special-case single values, as IN isn't terribly efficient
1760                                         // Don't necessarily assume the single key is 0; we don't
1761                                         // enforce linear numeric ordering on other arrays here.
1762                                         $value = array_values( $value );
1763                                         $list .= $field . " = " . $this->addQuotes( $value[0] );
1764                                 } else {
1765                                         $list .= $field . " IN (" . $this->makeList( $value ) . ") ";
1766                                 }
1767                         } elseif ( $value === null ) {
1768                                 if ( $mode == LIST_AND || $mode == LIST_OR ) {
1769                                         $list .= "$field IS ";
1770                                 } elseif ( $mode == LIST_SET ) {
1771                                         $list .= "$field = ";
1772                                 }
1773                                 $list .= 'NULL';
1774                         } else {
1775                                 if ( $mode == LIST_AND || $mode == LIST_OR || $mode == LIST_SET ) {
1776                                         $list .= "$field = ";
1777                                 }
1778                                 $list .= $mode == LIST_NAMES ? $value : $this->addQuotes( $value );
1779                         }
1780                 }
1781
1782                 return $list;
1783         }
1784
1785         /**
1786          * Build a partial where clause from a 2-d array such as used for LinkBatch.
1787          * The keys on each level may be either integers or strings.
1788          *
1789          * @param $data Array: organized as 2-d
1790          *              array(baseKeyVal => array(subKeyVal => [ignored], ...), ...)
1791          * @param $baseKey String: field name to match the base-level keys to (eg 'pl_namespace')
1792          * @param $subKey String: field name to match the sub-level keys to (eg 'pl_title')
1793          * @return Mixed: string SQL fragment, or false if no items in array.
1794          */
1795         public function makeWhereFrom2d( $data, $baseKey, $subKey ) {
1796                 $conds = array();
1797
1798                 foreach ( $data as $base => $sub ) {
1799                         if ( count( $sub ) ) {
1800                                 $conds[] = $this->makeList(
1801                                         array( $baseKey => $base, $subKey => array_keys( $sub ) ),
1802                                         LIST_AND );
1803                         }
1804                 }
1805
1806                 if ( $conds ) {
1807                         return $this->makeList( $conds, LIST_OR );
1808                 } else {
1809                         // Nothing to search for...
1810                         return false;
1811                 }
1812         }
1813
1814         /**
1815          * Return aggregated value alias
1816          *
1817          * @param $valuedata
1818          * @param $valuename string
1819          *
1820          * @return string
1821          */
1822         public function aggregateValue( $valuedata, $valuename = 'value' ) {
1823                 return $valuename;
1824         }
1825
1826         /**
1827          * @param $field
1828          * @return string
1829          */
1830         public function bitNot( $field ) {
1831                 return "(~$field)";
1832         }
1833
1834         /**
1835          * @param $fieldLeft
1836          * @param $fieldRight
1837          * @return string
1838          */
1839         public function bitAnd( $fieldLeft, $fieldRight ) {
1840                 return "($fieldLeft & $fieldRight)";
1841         }
1842
1843         /**
1844          * @param  $fieldLeft
1845          * @param  $fieldRight
1846          * @return string
1847          */
1848         public function bitOr( $fieldLeft, $fieldRight ) {
1849                 return "($fieldLeft | $fieldRight)";
1850         }
1851
1852         /**
1853          * Build a concatenation list to feed into a SQL query
1854          * @param $stringList Array: list of raw SQL expressions; caller is responsible for any quoting
1855          * @return String
1856          */
1857         public function buildConcat( $stringList ) {
1858                 return 'CONCAT(' . implode( ',', $stringList ) . ')';
1859         }
1860
1861         /**
1862          * Change the current database
1863          *
1864          * @todo Explain what exactly will fail if this is not overridden.
1865          *
1866          * @param $db
1867          *
1868          * @return bool Success or failure
1869          */
1870         public function selectDB( $db ) {
1871                 # Stub.  Shouldn't cause serious problems if it's not overridden, but
1872                 # if your database engine supports a concept similar to MySQL's
1873                 # databases you may as well.
1874                 $this->mDBname = $db;
1875                 return true;
1876         }
1877
1878         /**
1879          * Get the current DB name
1880          */
1881         public function getDBname() {
1882                 return $this->mDBname;
1883         }
1884
1885         /**
1886          * Get the server hostname or IP address
1887          */
1888         public function getServer() {
1889                 return $this->mServer;
1890         }
1891
1892         /**
1893          * Format a table name ready for use in constructing an SQL query
1894          *
1895          * This does two important things: it quotes the table names to clean them up,
1896          * and it adds a table prefix if only given a table name with no quotes.
1897          *
1898          * All functions of this object which require a table name call this function
1899          * themselves. Pass the canonical name to such functions. This is only needed
1900          * when calling query() directly.
1901          *
1902          * @param $name String: database table name
1903          * @param $format String One of:
1904          *   quoted - Automatically pass the table name through addIdentifierQuotes()
1905          *            so that it can be used in a query.
1906          *   raw - Do not add identifier quotes to the table name
1907          * @return String: full database name
1908          */
1909         public function tableName( $name, $format = 'quoted' ) {
1910                 global $wgSharedDB, $wgSharedPrefix, $wgSharedTables;
1911                 # Skip the entire process when we have a string quoted on both ends.
1912                 # Note that we check the end so that we will still quote any use of
1913                 # use of `database`.table. But won't break things if someone wants
1914                 # to query a database table with a dot in the name.
1915                 if ( $this->isQuotedIdentifier( $name ) ) {
1916                         return $name;
1917                 }
1918
1919                 # Lets test for any bits of text that should never show up in a table
1920                 # name. Basically anything like JOIN or ON which are actually part of
1921                 # SQL queries, but may end up inside of the table value to combine
1922                 # sql. Such as how the API is doing.
1923                 # Note that we use a whitespace test rather than a \b test to avoid
1924                 # any remote case where a word like on may be inside of a table name
1925                 # surrounded by symbols which may be considered word breaks.
1926                 if ( preg_match( '/(^|\s)(DISTINCT|JOIN|ON|AS)(\s|$)/i', $name ) !== 0 ) {
1927                         return $name;
1928                 }
1929
1930                 # Split database and table into proper variables.
1931                 # We reverse the explode so that database.table and table both output
1932                 # the correct table.
1933                 $dbDetails = array_reverse( explode( '.', $name, 2 ) );
1934                 if ( isset( $dbDetails[1] ) ) {
1935                         list( $table, $database ) = $dbDetails;
1936                 } else {
1937                         list( $table ) = $dbDetails;
1938                 }
1939                 $prefix = $this->mTablePrefix; # Default prefix
1940
1941                 # A database name has been specified in input. We don't want any
1942                 # prefixes added.
1943                 if ( isset( $database ) ) {
1944                         $prefix = '';
1945                 }
1946
1947                 # Note that we use the long format because php will complain in in_array if
1948                 # the input is not an array, and will complain in is_array if it is not set.
1949                 if ( !isset( $database ) # Don't use shared database if pre selected.
1950                  && isset( $wgSharedDB ) # We have a shared database
1951                  && !$this->isQuotedIdentifier( $table ) # Paranoia check to prevent shared tables listing '`table`'
1952                  && isset( $wgSharedTables )
1953                  && is_array( $wgSharedTables )
1954                  && in_array( $table, $wgSharedTables ) ) { # A shared table is selected
1955                         $database = $wgSharedDB;
1956                         $prefix   = isset( $wgSharedPrefix ) ? $wgSharedPrefix : $prefix;
1957                 }
1958
1959                 # Quote the $database and $table and apply the prefix if not quoted.
1960                 if ( isset( $database ) ) {
1961                         if ( $format == 'quoted' && !$this->isQuotedIdentifier( $database ) ) {
1962                                 $database = $this->addIdentifierQuotes( $database );
1963                         }
1964                 }
1965
1966                 $table = "{$prefix}{$table}";
1967                 if ( $format == 'quoted' && !$this->isQuotedIdentifier( $table ) ) {
1968                         $table = $this->addIdentifierQuotes( "{$table}" );
1969                 }
1970
1971                 # Merge our database and table into our final table name.
1972                 $tableName = ( isset( $database ) ? "{$database}.{$table}" : "{$table}" );
1973
1974                 return $tableName;
1975         }
1976
1977         /**
1978          * Fetch a number of table names into an array
1979          * This is handy when you need to construct SQL for joins
1980          *
1981          * Example:
1982          * extract($dbr->tableNames('user','watchlist'));
1983          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
1984          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
1985          *
1986          * @return array
1987          */
1988         public function tableNames() {
1989                 $inArray = func_get_args();
1990                 $retVal = array();
1991
1992                 foreach ( $inArray as $name ) {
1993                         $retVal[$name] = $this->tableName( $name );
1994                 }
1995
1996                 return $retVal;
1997         }
1998
1999         /**
2000          * Fetch a number of table names into an zero-indexed numerical array
2001          * This is handy when you need to construct SQL for joins
2002          *
2003          * Example:
2004          * list( $user, $watchlist ) = $dbr->tableNamesN('user','watchlist');
2005          * $sql = "SELECT wl_namespace,wl_title FROM $watchlist,$user
2006          *         WHERE wl_user=user_id AND wl_user=$nameWithQuotes";
2007          *
2008          * @return array
2009          */
2010         public function tableNamesN() {
2011                 $inArray = func_get_args();
2012                 $retVal = array();
2013
2014                 foreach ( $inArray as $name ) {
2015                         $retVal[] = $this->tableName( $name );
2016                 }
2017
2018                 return $retVal;
2019         }
2020
2021         /**
2022          * Get an aliased table name
2023          * e.g. tableName AS newTableName
2024          *
2025          * @param $name string Table name, see tableName()
2026          * @param $alias string|bool Alias (optional)
2027          * @return string SQL name for aliased table. Will not alias a table to its own name
2028          */
2029         public function tableNameWithAlias( $name, $alias = false ) {
2030                 if ( !$alias || $alias == $name ) {
2031                         return $this->tableName( $name );
2032                 } else {
2033                         return $this->tableName( $name ) . ' ' . $this->addIdentifierQuotes( $alias );
2034                 }
2035         }
2036
2037         /**
2038          * Gets an array of aliased table names
2039          *
2040          * @param $tables array( [alias] => table )
2041          * @return array of strings, see tableNameWithAlias()
2042          */
2043         public function tableNamesWithAlias( $tables ) {
2044                 $retval = array();
2045                 foreach ( $tables as $alias => $table ) {
2046                         if ( is_numeric( $alias ) ) {
2047                                 $alias = $table;
2048                         }
2049                         $retval[] = $this->tableNameWithAlias( $table, $alias );
2050                 }
2051                 return $retval;
2052         }
2053
2054         /**
2055          * Get an aliased field name
2056          * e.g. fieldName AS newFieldName
2057          *
2058          * @param $name string Field name
2059          * @param $alias string|bool Alias (optional)
2060          * @return string SQL name for aliased field. Will not alias a field to its own name
2061          */
2062         public function fieldNameWithAlias( $name, $alias = false ) {
2063                 if ( !$alias || (string)$alias === (string)$name ) {
2064                         return $name;
2065                 } else {
2066                         return $name . ' AS ' . $alias; //PostgreSQL needs AS
2067                 }
2068         }
2069
2070         /**
2071          * Gets an array of aliased field names
2072          *
2073          * @param $fields array( [alias] => field )
2074          * @return array of strings, see fieldNameWithAlias()
2075          */
2076         public function fieldNamesWithAlias( $fields ) {
2077                 $retval = array();
2078                 foreach ( $fields as $alias => $field ) {
2079                         if ( is_numeric( $alias ) ) {
2080                                 $alias = $field;
2081                         }
2082                         $retval[] = $this->fieldNameWithAlias( $field, $alias );
2083                 }
2084                 return $retval;
2085         }
2086
2087         /**
2088          * Get the aliased table name clause for a FROM clause
2089          * which might have a JOIN and/or USE INDEX clause
2090          *
2091          * @param $tables array ( [alias] => table )
2092          * @param $use_index array Same as for select()
2093          * @param $join_conds array Same as for select()
2094          * @return string
2095          */
2096         protected function tableNamesWithUseIndexOrJOIN(
2097                 $tables, $use_index = array(), $join_conds = array()
2098         ) {
2099                 $ret = array();
2100                 $retJOIN = array();
2101                 $use_index = (array)$use_index;
2102                 $join_conds = (array)$join_conds;
2103
2104                 foreach ( $tables as $alias => $table ) {
2105                         if ( !is_string( $alias ) ) {
2106                                 // No alias? Set it equal to the table name
2107                                 $alias = $table;
2108                         }
2109                         // Is there a JOIN clause for this table?
2110                         if ( isset( $join_conds[$alias] ) ) {
2111                                 list( $joinType, $conds ) = $join_conds[$alias];
2112                                 $tableClause = $joinType;
2113                                 $tableClause .= ' ' . $this->tableNameWithAlias( $table, $alias );
2114                                 if ( isset( $use_index[$alias] ) ) { // has USE INDEX?
2115                                         $use = $this->useIndexClause( implode( ',', (array)$use_index[$alias] ) );
2116                                         if ( $use != '' ) {
2117                                                 $tableClause .= ' ' . $use;
2118                                         }
2119                                 }
2120                                 $on = $this->makeList( (array)$conds, LIST_AND );
2121                                 if ( $on != '' ) {
2122                                         $tableClause .= ' ON (' . $on . ')';
2123                                 }
2124
2125                                 $retJOIN[] = $tableClause;
2126                         // Is there an INDEX clause for this table?
2127                         } elseif ( isset( $use_index[$alias] ) ) {
2128                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2129                                 $tableClause .= ' ' . $this->useIndexClause(
2130                                         implode( ',', (array)$use_index[$alias] ) );
2131
2132                                 $ret[] = $tableClause;
2133                         } else {
2134                                 $tableClause = $this->tableNameWithAlias( $table, $alias );
2135
2136                                 $ret[] = $tableClause;
2137                         }
2138                 }
2139
2140                 // We can't separate explicit JOIN clauses with ',', use ' ' for those
2141                 $straightJoins = !empty( $ret ) ? implode( ',', $ret ) : "";
2142                 $otherJoins = !empty( $retJOIN ) ? implode( ' ', $retJOIN ) : "";
2143
2144                 // Compile our final table clause
2145                 return implode( ' ', array( $straightJoins, $otherJoins ) );
2146         }
2147
2148         /**
2149          * Get the name of an index in a given table
2150          *
2151          * @param $index
2152          *
2153          * @return string
2154          */
2155         protected function indexName( $index ) {
2156                 // Backwards-compatibility hack
2157                 $renamed = array(
2158                         'ar_usertext_timestamp' => 'usertext_timestamp',
2159                         'un_user_id'            => 'user_id',
2160                         'un_user_ip'            => 'user_ip',
2161                 );
2162
2163                 if ( isset( $renamed[$index] ) ) {
2164                         return $renamed[$index];
2165                 } else {
2166                         return $index;
2167                 }
2168         }
2169
2170         /**
2171          * If it's a string, adds quotes and backslashes
2172          * Otherwise returns as-is
2173          *
2174          * @param $s string
2175          *
2176          * @return string
2177          */
2178         public function addQuotes( $s ) {
2179                 if ( $s === null ) {
2180                         return 'NULL';
2181                 } else {
2182                         # This will also quote numeric values. This should be harmless,
2183                         # and protects against weird problems that occur when they really
2184                         # _are_ strings such as article titles and string->number->string
2185                         # conversion is not 1:1.
2186                         return "'" . $this->strencode( $s ) . "'";
2187                 }
2188         }
2189
2190         /**
2191          * Quotes an identifier using `backticks` or "double quotes" depending on the database type.
2192          * MySQL uses `backticks` while basically everything else uses double quotes.
2193          * Since MySQL is the odd one out here the double quotes are our generic
2194          * and we implement backticks in DatabaseMysql.
2195          *
2196          * @param $s string
2197          *
2198          * @return string
2199          */
2200         public function addIdentifierQuotes( $s ) {
2201                 return '"' . str_replace( '"', '""', $s ) . '"';
2202         }
2203
2204         /**
2205          * Returns if the given identifier looks quoted or not according to
2206          * the database convention for quoting identifiers .
2207          *
2208          * @param $name string
2209          *
2210          * @return boolean
2211          */
2212         public function isQuotedIdentifier( $name ) {
2213                 return $name[0] == '"' && substr( $name, -1, 1 ) == '"';
2214         }
2215
2216         /**
2217          * @param $s string
2218          * @return string
2219          */
2220         protected function escapeLikeInternal( $s ) {
2221                 $s = str_replace( '\\', '\\\\', $s );
2222                 $s = $this->strencode( $s );
2223                 $s = str_replace( array( '%', '_' ), array( '\%', '\_' ), $s );
2224
2225                 return $s;
2226         }
2227
2228         /**
2229          * LIKE statement wrapper, receives a variable-length argument list with parts of pattern to match
2230          * containing either string literals that will be escaped or tokens returned by anyChar() or anyString().
2231          * Alternatively, the function could be provided with an array of aforementioned parameters.
2232          *
2233          * Example: $dbr->buildLike( 'My_page_title/', $dbr->anyString() ) returns a LIKE clause that searches
2234          * for subpages of 'My page title'.
2235          * Alternatively: $pattern = array( 'My_page_title/', $dbr->anyString() ); $query .= $dbr->buildLike( $pattern );
2236          *
2237          * @since 1.16
2238          * @return String: fully built LIKE statement
2239          */
2240         public function buildLike() {
2241                 $params = func_get_args();
2242
2243                 if ( count( $params ) > 0 && is_array( $params[0] ) ) {
2244                         $params = $params[0];
2245                 }
2246
2247                 $s = '';
2248
2249                 foreach ( $params as $value ) {
2250                         if ( $value instanceof LikeMatch ) {
2251                                 $s .= $value->toString();
2252                         } else {
2253                                 $s .= $this->escapeLikeInternal( $value );
2254                         }
2255                 }
2256
2257                 return " LIKE '" . $s . "' ";
2258         }
2259
2260         /**
2261          * Returns a token for buildLike() that denotes a '_' to be used in a LIKE query
2262          *
2263          * @return LikeMatch
2264          */
2265         public function anyChar() {
2266                 return new LikeMatch( '_' );
2267         }
2268
2269         /**
2270          * Returns a token for buildLike() that denotes a '%' to be used in a LIKE query
2271          *
2272          * @return LikeMatch
2273          */
2274         public function anyString() {
2275                 return new LikeMatch( '%' );
2276         }
2277
2278         /**
2279          * Returns an appropriately quoted sequence value for inserting a new row.
2280          * MySQL has autoincrement fields, so this is just NULL. But the PostgreSQL
2281          * subclass will return an integer, and save the value for insertId()
2282          *
2283          * Any implementation of this function should *not* involve reusing
2284          * sequence numbers created for rolled-back transactions.
2285          * See http://bugs.mysql.com/bug.php?id=30767 for details.
2286          * @param $seqName string
2287          * @return null
2288          */
2289         public function nextSequenceValue( $seqName ) {
2290                 return null;
2291         }
2292
2293         /**
2294          * USE INDEX clause.  Unlikely to be useful for anything but MySQL.  This
2295          * is only needed because a) MySQL must be as efficient as possible due to
2296          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2297          * which index to pick.  Anyway, other databases might have different
2298          * indexes on a given table.  So don't bother overriding this unless you're
2299          * MySQL.
2300          * @param $index
2301          * @return string
2302          */
2303         public function useIndexClause( $index ) {
2304                 return '';
2305         }
2306
2307         /**
2308          * REPLACE query wrapper.
2309          *
2310          * REPLACE is a very handy MySQL extension, which functions like an INSERT
2311          * except that when there is a duplicate key error, the old row is deleted
2312          * and the new row is inserted in its place.
2313          *
2314          * We simulate this with standard SQL with a DELETE followed by INSERT. To
2315          * perform the delete, we need to know what the unique indexes are so that
2316          * we know how to find the conflicting rows.
2317          *
2318          * It may be more efficient to leave off unique indexes which are unlikely
2319          * to collide. However if you do this, you run the risk of encountering
2320          * errors which wouldn't have occurred in MySQL.
2321          *
2322          * @param $table String: The table to replace the row(s) in.
2323          * @param $rows array Can be either a single row to insert, or multiple rows,
2324          *    in the same format as for DatabaseBase::insert()
2325          * @param $uniqueIndexes array is an array of indexes. Each element may be either
2326          *    a field name or an array of field names
2327          * @param $fname String: Calling function name (use __METHOD__) for logs/profiling
2328          */
2329         public function replace( $table, $uniqueIndexes, $rows, $fname = 'DatabaseBase::replace' ) {
2330                 $quotedTable = $this->tableName( $table );
2331
2332                 if ( count( $rows ) == 0 ) {
2333                         return;
2334                 }
2335
2336                 # Single row case
2337                 if ( !is_array( reset( $rows ) ) ) {
2338                         $rows = array( $rows );
2339                 }
2340
2341                 foreach( $rows as $row ) {
2342                         # Delete rows which collide
2343                         if ( $uniqueIndexes ) {
2344                                 $sql = "DELETE FROM $quotedTable WHERE ";
2345                                 $first = true;
2346                                 foreach ( $uniqueIndexes as $index ) {
2347                                         if ( $first ) {
2348                                                 $first = false;
2349                                                 $sql .= '( ';
2350                                         } else {
2351                                                 $sql .= ' ) OR ( ';
2352                                         }
2353                                         if ( is_array( $index ) ) {
2354                                                 $first2 = true;
2355                                                 foreach ( $index as $col ) {
2356                                                         if ( $first2 ) {
2357                                                                 $first2 = false;
2358                                                         } else {
2359                                                                 $sql .= ' AND ';
2360                                                         }
2361                                                         $sql .= $col . '=' . $this->addQuotes( $row[$col] );
2362                                                 }
2363                                         } else {
2364                                                 $sql .= $index . '=' . $this->addQuotes( $row[$index] );
2365                                         }
2366                                 }
2367                                 $sql .= ' )';
2368                                 $this->query( $sql, $fname );
2369                         }
2370
2371                         # Now insert the row
2372                         $this->insert( $table, $row );
2373                 }
2374         }
2375
2376         /**
2377          * REPLACE query wrapper for MySQL and SQLite, which have a native REPLACE
2378          * statement.
2379          *
2380          * @param $table string Table name
2381          * @param $rows array Rows to insert
2382          * @param $fname string Caller function name
2383          *
2384          * @return ResultWrapper
2385          */
2386         protected function nativeReplace( $table, $rows, $fname ) {
2387                 $table = $this->tableName( $table );
2388
2389                 # Single row case
2390                 if ( !is_array( reset( $rows ) ) ) {
2391                         $rows = array( $rows );
2392                 }
2393
2394                 $sql = "REPLACE INTO $table (" . implode( ',', array_keys( $rows[0] ) ) . ') VALUES ';
2395                 $first = true;
2396
2397                 foreach ( $rows as $row ) {
2398                         if ( $first ) {
2399                                 $first = false;
2400                         } else {
2401                                 $sql .= ',';
2402                         }
2403
2404                         $sql .= '(' . $this->makeList( $row ) . ')';
2405                 }
2406
2407                 return $this->query( $sql, $fname );
2408         }
2409
2410         /**
2411          * DELETE where the condition is a join.
2412          *
2413          * MySQL overrides this to use a multi-table DELETE syntax, in other databases
2414          * we use sub-selects
2415          *
2416          * For safety, an empty $conds will not delete everything. If you want to
2417          * delete all rows where the join condition matches, set $conds='*'.
2418          *
2419          * DO NOT put the join condition in $conds.
2420          *
2421          * @param $delTable   String: The table to delete from.
2422          * @param $joinTable  String: The other table.
2423          * @param $delVar     String: The variable to join on, in the first table.
2424          * @param $joinVar    String: The variable to join on, in the second table.
2425          * @param $conds      Array: Condition array of field names mapped to variables,
2426          *                    ANDed together in the WHERE clause
2427          * @param $fname      String: Calling function name (use __METHOD__) for
2428          *                    logs/profiling
2429          */
2430         public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
2431                 $fname = 'DatabaseBase::deleteJoin' )
2432         {
2433                 if ( !$conds ) {
2434                         throw new DBUnexpectedError( $this,
2435                                 'DatabaseBase::deleteJoin() called with empty $conds' );
2436                 }
2437
2438                 $delTable = $this->tableName( $delTable );
2439                 $joinTable = $this->tableName( $joinTable );
2440                 $sql = "DELETE FROM $delTable WHERE $delVar IN (SELECT $joinVar FROM $joinTable ";
2441                 if ( $conds != '*' ) {
2442                         $sql .= 'WHERE ' . $this->makeList( $conds, LIST_AND );
2443                 }
2444                 $sql .= ')';
2445
2446                 $this->query( $sql, $fname );
2447         }
2448
2449         /**
2450          * Returns the size of a text field, or -1 for "unlimited"
2451          *
2452          * @param $table string
2453          * @param $field string
2454          *
2455          * @return int
2456          */
2457         public function textFieldSize( $table, $field ) {
2458                 $table = $this->tableName( $table );
2459                 $sql = "SHOW COLUMNS FROM $table LIKE \"$field\";";
2460                 $res = $this->query( $sql, 'DatabaseBase::textFieldSize' );
2461                 $row = $this->fetchObject( $res );
2462
2463                 $m = array();
2464
2465                 if ( preg_match( '/\((.*)\)/', $row->Type, $m ) ) {
2466                         $size = $m[1];
2467                 } else {
2468                         $size = -1;
2469                 }
2470
2471                 return $size;
2472         }
2473
2474         /**
2475          * A string to insert into queries to show that they're low-priority, like
2476          * MySQL's LOW_PRIORITY.  If no such feature exists, return an empty
2477          * string and nothing bad should happen.
2478          *
2479          * @return string Returns the text of the low priority option if it is
2480          *   supported, or a blank string otherwise
2481          */
2482         public function lowPriorityOption() {
2483                 return '';
2484         }
2485
2486         /**
2487          * DELETE query wrapper.
2488          *
2489          * @param $table Array Table name
2490          * @param $conds String|Array of conditions. See $conds in DatabaseBase::select() for
2491          *               the format. Use $conds == "*" to delete all rows
2492          * @param $fname String name of the calling function
2493          *
2494          * @return bool
2495          */
2496         public function delete( $table, $conds, $fname = 'DatabaseBase::delete' ) {
2497                 if ( !$conds ) {
2498                         throw new DBUnexpectedError( $this, 'DatabaseBase::delete() called with no conditions' );
2499                 }
2500
2501                 $table = $this->tableName( $table );
2502                 $sql = "DELETE FROM $table";
2503
2504                 if ( $conds != '*' ) {
2505                         $sql .= ' WHERE ' . $this->makeList( $conds, LIST_AND );
2506                 }
2507
2508                 return $this->query( $sql, $fname );
2509         }
2510
2511         /**
2512          * INSERT SELECT wrapper. Takes data from a SELECT query and inserts it
2513          * into another table.
2514          *
2515          * @param $destTable string The table name to insert into
2516          * @param $srcTable string|array May be either a table name, or an array of table names
2517          *    to include in a join.
2518          *
2519          * @param $varMap array must be an associative array of the form
2520          *    array( 'dest1' => 'source1', ...). Source items may be literals
2521          *    rather than field names, but strings should be quoted with
2522          *    DatabaseBase::addQuotes()
2523          *
2524          * @param $conds array Condition array. See $conds in DatabaseBase::select() for
2525          *    the details of the format of condition arrays. May be "*" to copy the
2526          *    whole table.
2527          *
2528          * @param $fname string The function name of the caller, from __METHOD__
2529          *
2530          * @param $insertOptions array Options for the INSERT part of the query, see
2531          *    DatabaseBase::insert() for details.
2532          * @param $selectOptions array Options for the SELECT part of the query, see
2533          *    DatabaseBase::select() for details.
2534          *
2535          * @return ResultWrapper
2536          */
2537         public function insertSelect( $destTable, $srcTable, $varMap, $conds,
2538                 $fname = 'DatabaseBase::insertSelect',
2539                 $insertOptions = array(), $selectOptions = array() )
2540         {
2541                 $destTable = $this->tableName( $destTable );
2542
2543                 if ( is_array( $insertOptions ) ) {
2544                         $insertOptions = implode( ' ', $insertOptions );
2545                 }
2546
2547                 if ( !is_array( $selectOptions ) ) {
2548                         $selectOptions = array( $selectOptions );
2549                 }
2550
2551                 list( $startOpts, $useIndex, $tailOpts ) = $this->makeSelectOptions( $selectOptions );
2552
2553                 if ( is_array( $srcTable ) ) {
2554                         $srcTable =  implode( ',', array_map( array( &$this, 'tableName' ), $srcTable ) );
2555                 } else {
2556                         $srcTable = $this->tableName( $srcTable );
2557                 }
2558
2559                 $sql = "INSERT $insertOptions INTO $destTable (" . implode( ',', array_keys( $varMap ) ) . ')' .
2560                         " SELECT $startOpts " . implode( ',', $varMap ) .
2561                         " FROM $srcTable $useIndex ";
2562
2563                 if ( $conds != '*' ) {
2564                         if ( is_array( $conds ) ) {
2565                                 $conds = $this->makeList( $conds, LIST_AND );
2566                         }
2567                         $sql .= " WHERE $conds";
2568                 }
2569
2570                 $sql .= " $tailOpts";
2571
2572                 return $this->query( $sql, $fname );
2573         }
2574
2575         /**
2576          * Construct a LIMIT query with optional offset.  This is used for query
2577          * pages.  The SQL should be adjusted so that only the first $limit rows
2578          * are returned.  If $offset is provided as well, then the first $offset
2579          * rows should be discarded, and the next $limit rows should be returned.
2580          * If the result of the query is not ordered, then the rows to be returned
2581          * are theoretically arbitrary.
2582          *
2583          * $sql is expected to be a SELECT, if that makes a difference.
2584          *
2585          * The version provided by default works in MySQL and SQLite.  It will very
2586          * likely need to be overridden for most other DBMSes.
2587          *
2588          * @param $sql String SQL query we will append the limit too
2589          * @param $limit Integer the SQL limit
2590          * @param $offset Integer|bool the SQL offset (default false)
2591          *
2592          * @return string
2593          */
2594         public function limitResult( $sql, $limit, $offset = false ) {
2595                 if ( !is_numeric( $limit ) ) {
2596                         throw new DBUnexpectedError( $this, "Invalid non-numeric limit passed to limitResult()\n" );
2597                 }
2598                 return "$sql LIMIT "
2599                         . ( ( is_numeric( $offset ) && $offset != 0 ) ? "{$offset}," : "" )
2600                         . "{$limit} ";
2601         }
2602
2603         /**
2604          * Returns true if current database backend supports ORDER BY or LIMIT for separate subqueries
2605          * within the UNION construct.
2606          * @return Boolean
2607          */
2608         public function unionSupportsOrderAndLimit() {
2609                 return true; // True for almost every DB supported
2610         }
2611
2612         /**
2613          * Construct a UNION query
2614          * This is used for providing overload point for other DB abstractions
2615          * not compatible with the MySQL syntax.
2616          * @param $sqls Array: SQL statements to combine
2617          * @param $all Boolean: use UNION ALL
2618          * @return String: SQL fragment
2619          */
2620         public function unionQueries( $sqls, $all ) {
2621                 $glue = $all ? ') UNION ALL (' : ') UNION (';
2622                 return '(' . implode( $glue, $sqls ) . ')';
2623         }
2624
2625         /**
2626          * Returns an SQL expression for a simple conditional.  This doesn't need
2627          * to be overridden unless CASE isn't supported in your DBMS.
2628          *
2629          * @param $cond string|array SQL expression which will result in a boolean value
2630          * @param $trueVal String: SQL expression to return if true
2631          * @param $falseVal String: SQL expression to return if false
2632          * @return String: SQL fragment
2633          */
2634         public function conditional( $cond, $trueVal, $falseVal ) {
2635                 if ( is_array( $cond ) ) {
2636                         $cond = $this->makeList( $cond, LIST_AND );
2637                 }
2638                 return " (CASE WHEN $cond THEN $trueVal ELSE $falseVal END) ";
2639         }
2640
2641         /**
2642          * Returns a comand for str_replace function in SQL query.
2643          * Uses REPLACE() in MySQL
2644          *
2645          * @param $orig String: column to modify
2646          * @param $old String: column to seek
2647          * @param $new String: column to replace with
2648          *
2649          * @return string
2650          */
2651         public function strreplace( $orig, $old, $new ) {
2652                 return "REPLACE({$orig}, {$old}, {$new})";
2653         }
2654
2655         /**
2656          * Determines how long the server has been up
2657          * STUB
2658          *
2659          * @return int
2660          */
2661         public function getServerUptime() {
2662                 return 0;
2663         }
2664
2665         /**
2666          * Determines if the last failure was due to a deadlock
2667          * STUB
2668          *
2669          * @return bool
2670          */
2671         public function wasDeadlock() {
2672                 return false;
2673         }
2674
2675         /**
2676          * Determines if the last failure was due to a lock timeout
2677          * STUB
2678          *
2679          * @return bool
2680          */
2681         public function wasLockTimeout() {
2682                 return false;
2683         }
2684
2685         /**
2686          * Determines if the last query error was something that should be dealt
2687          * with by pinging the connection and reissuing the query.
2688          * STUB
2689          *
2690          * @return bool
2691          */
2692         public function wasErrorReissuable() {
2693                 return false;
2694         }
2695
2696         /**
2697          * Determines if the last failure was due to the database being read-only.
2698          * STUB
2699          *
2700          * @return bool
2701          */
2702         public function wasReadOnlyError() {
2703                 return false;
2704         }
2705
2706         /**
2707          * Perform a deadlock-prone transaction.
2708          *
2709          * This function invokes a callback function to perform a set of write
2710          * queries. If a deadlock occurs during the processing, the transaction
2711          * will be rolled back and the callback function will be called again.
2712          *
2713          * Usage:
2714          *   $dbw->deadlockLoop( callback, ... );
2715          *
2716          * Extra arguments are passed through to the specified callback function.
2717          *
2718          * Returns whatever the callback function returned on its successful,
2719          * iteration, or false on error, for example if the retry limit was
2720          * reached.
2721          *
2722          * @return bool
2723          */
2724         public function deadlockLoop() {
2725                 $this->begin( __METHOD__ );
2726                 $args = func_get_args();
2727                 $function = array_shift( $args );
2728                 $oldIgnore = $this->ignoreErrors( true );
2729                 $tries = DEADLOCK_TRIES;
2730
2731                 if ( is_array( $function ) ) {
2732                         $fname = $function[0];
2733                 } else {
2734                         $fname = $function;
2735                 }
2736
2737                 do {
2738                         $retVal = call_user_func_array( $function, $args );
2739                         $error = $this->lastError();
2740                         $errno = $this->lastErrno();
2741                         $sql = $this->lastQuery();
2742
2743                         if ( $errno ) {
2744                                 if ( $this->wasDeadlock() ) {
2745                                         # Retry
2746                                         usleep( mt_rand( DEADLOCK_DELAY_MIN, DEADLOCK_DELAY_MAX ) );
2747                                 } else {
2748                                         $this->reportQueryError( $error, $errno, $sql, $fname );
2749                                 }
2750                         }
2751                 } while ( $this->wasDeadlock() && --$tries > 0 );
2752
2753                 $this->ignoreErrors( $oldIgnore );
2754
2755                 if ( $tries <= 0 ) {
2756                         $this->rollback( __METHOD__ );
2757                         $this->reportQueryError( $error, $errno, $sql, $fname );
2758                         return false;
2759                 } else {
2760                         $this->commit( __METHOD__ );
2761                         return $retVal;
2762                 }
2763         }
2764
2765         /**
2766          * Wait for the slave to catch up to a given master position.
2767          *
2768          * @param $pos DBMasterPos object
2769          * @param $timeout Integer: the maximum number of seconds to wait for
2770          *   synchronisation
2771          *
2772          * @return integer: zero if the slave was past that position already,
2773          *   greater than zero if we waited for some period of time, less than
2774          *   zero if we timed out.
2775          */
2776         public function masterPosWait( DBMasterPos $pos, $timeout ) {
2777                 wfProfileIn( __METHOD__ );
2778
2779                 if ( !is_null( $this->mFakeSlaveLag ) ) {
2780                         $wait = intval( ( $pos->pos - microtime( true ) + $this->mFakeSlaveLag ) * 1e6 );
2781
2782                         if ( $wait > $timeout * 1e6 ) {
2783                                 wfDebug( "Fake slave timed out waiting for $pos ($wait us)\n" );
2784                                 wfProfileOut( __METHOD__ );
2785                                 return -1;
2786                         } elseif ( $wait > 0 ) {
2787                                 wfDebug( "Fake slave waiting $wait us\n" );
2788                                 usleep( $wait );
2789                                 wfProfileOut( __METHOD__ );
2790                                 return 1;
2791                         } else {
2792                                 wfDebug( "Fake slave up to date ($wait us)\n" );
2793                                 wfProfileOut( __METHOD__ );
2794                                 return 0;
2795                         }
2796                 }
2797
2798                 wfProfileOut( __METHOD__ );
2799
2800                 # Real waits are implemented in the subclass.
2801                 return 0;
2802         }
2803
2804         /**
2805          * Get the replication position of this slave
2806          *
2807          * @return DBMasterPos, or false if this is not a slave.
2808          */
2809         public function getSlavePos() {
2810                 if ( !is_null( $this->mFakeSlaveLag ) ) {
2811                         $pos = new MySQLMasterPos( 'fake', microtime( true ) - $this->mFakeSlaveLag );
2812                         wfDebug( __METHOD__ . ": fake slave pos = $pos\n" );
2813                         return $pos;
2814                 } else {
2815                         # Stub
2816                         return false;
2817                 }
2818         }
2819
2820         /**
2821          * Get the position of this master
2822          *
2823          * @return DBMasterPos, or false if this is not a master
2824          */
2825         public function getMasterPos() {
2826                 if ( $this->mFakeMaster ) {
2827                         return new MySQLMasterPos( 'fake', microtime( true ) );
2828                 } else {
2829                         return false;
2830                 }
2831         }
2832
2833         /**
2834          * Run an anonymous function as soon as there is no transaction pending.
2835          * If there is a transaction and it is rolled back, then the callback is cancelled.
2836          * Callbacks must commit any transactions that they begin.
2837          *
2838          * This is useful for updates to different systems or separate transactions are needed.
2839          *
2840          * @param Closure $callback
2841          * @return void
2842          */
2843         final public function onTransactionIdle( Closure $callback ) {
2844                 if ( $this->mTrxLevel ) {
2845                         $this->trxIdleCallbacks[] = $callback;
2846                 } else {
2847                         $callback();
2848                 }
2849         }
2850
2851         /**
2852          * Actually run the "on transaction idle" callbacks
2853          */
2854         protected function runOnTransactionIdleCallbacks() {
2855                 $e = null; // last exception
2856                 do { // callbacks may add callbacks :)
2857                         $callbacks = $this->trxIdleCallbacks;
2858                         $this->trxIdleCallbacks = array(); // recursion guard
2859                         foreach ( $callbacks as $callback ) {
2860                                 try {
2861                                         $callback();
2862                                 } catch ( Exception $e ) {}
2863                         }
2864                 } while ( count( $this->trxIdleCallbacks ) );
2865
2866                 if ( $e instanceof Exception ) {
2867                         throw $e; // re-throw any last exception
2868                 }
2869         }
2870
2871         /**
2872          * Begin a transaction
2873          *
2874          * @param $fname string
2875          */
2876         final public function begin( $fname = 'DatabaseBase::begin' ) {
2877                 if ( $this->mTrxLevel ) { // implicit commit
2878                         $this->doCommit( $fname );
2879                         $this->runOnTransactionIdleCallbacks();
2880                 }
2881                 $this->doBegin( $fname );
2882         }
2883
2884         /**
2885          * @see DatabaseBase::begin()
2886          * @param type $fname
2887          */
2888         protected function doBegin( $fname ) {
2889                 $this->query( 'BEGIN', $fname );
2890                 $this->mTrxLevel = 1;
2891         }
2892
2893         /**
2894          * End a transaction
2895          *
2896          * @param $fname string
2897          */
2898         final public function commit( $fname = 'DatabaseBase::commit' ) {
2899                 $this->doCommit( $fname );
2900                 $this->runOnTransactionIdleCallbacks();
2901         }
2902
2903         /**
2904          * @see DatabaseBase::commit()
2905          * @param type $fname
2906          */
2907         protected function doCommit( $fname ) {
2908                 if ( $this->mTrxLevel ) {
2909                         $this->query( 'COMMIT', $fname );
2910                         $this->mTrxLevel = 0;
2911                 }
2912         }
2913
2914         /**
2915          * Rollback a transaction.
2916          * No-op on non-transactional databases.
2917          *
2918          * @param $fname string
2919          */
2920         final public function rollback( $fname = 'DatabaseBase::rollback' ) {
2921                 $this->doRollback( $fname );
2922                 $this->trxIdleCallbacks = array(); // cancel
2923         }
2924
2925         /**
2926          * @see DatabaseBase::rollback()
2927          * @param type $fname
2928          */
2929         protected function doRollback( $fname ) {
2930                 if ( $this->mTrxLevel ) {
2931                         $this->query( 'ROLLBACK', $fname, true );
2932                         $this->mTrxLevel = 0;
2933                 }
2934         }
2935
2936         /**
2937          * Creates a new table with structure copied from existing table
2938          * Note that unlike most database abstraction functions, this function does not
2939          * automatically append database prefix, because it works at a lower
2940          * abstraction level.
2941          * The table names passed to this function shall not be quoted (this
2942          * function calls addIdentifierQuotes when needed).
2943          *
2944          * @param $oldName String: name of table whose structure should be copied
2945          * @param $newName String: name of table to be created
2946          * @param $temporary Boolean: whether the new table should be temporary
2947          * @param $fname String: calling function name
2948          * @return Boolean: true if operation was successful
2949          */
2950         public function duplicateTableStructure( $oldName, $newName, $temporary = false,
2951                 $fname = 'DatabaseBase::duplicateTableStructure' )
2952         {
2953                 throw new MWException(
2954                         'DatabaseBase::duplicateTableStructure is not implemented in descendant class' );
2955         }
2956
2957         /**
2958          * List all tables on the database
2959          *
2960          * @param $prefix string Only show tables with this prefix, e.g. mw_
2961          * @param $fname String: calling function name
2962          */
2963         function listTables( $prefix = null, $fname = 'DatabaseBase::listTables' ) {
2964                 throw new MWException( 'DatabaseBase::listTables is not implemented in descendant class' );
2965         }
2966
2967         /**
2968          * Convert a timestamp in one of the formats accepted by wfTimestamp()
2969          * to the format used for inserting into timestamp fields in this DBMS.
2970          *
2971          * The result is unquoted, and needs to be passed through addQuotes()
2972          * before it can be included in raw SQL.
2973          *
2974          * @param $ts string|int
2975          *
2976          * @return string
2977          */
2978         public function timestamp( $ts = 0 ) {
2979                 return wfTimestamp( TS_MW, $ts );
2980         }
2981
2982         /**
2983          * Convert a timestamp in one of the formats accepted by wfTimestamp()
2984          * to the format used for inserting into timestamp fields in this DBMS. If
2985          * NULL is input, it is passed through, allowing NULL values to be inserted
2986          * into timestamp fields.
2987          *
2988          * The result is unquoted, and needs to be passed through addQuotes()
2989          * before it can be included in raw SQL.
2990          *
2991          * @param $ts string|int
2992          *
2993          * @return string
2994          */
2995         public function timestampOrNull( $ts = null ) {
2996                 if ( is_null( $ts ) ) {
2997                         return null;
2998                 } else {
2999                         return $this->timestamp( $ts );
3000                 }
3001         }
3002
3003         /**
3004          * Take the result from a query, and wrap it in a ResultWrapper if
3005          * necessary. Boolean values are passed through as is, to indicate success
3006          * of write queries or failure.
3007          *
3008          * Once upon a time, DatabaseBase::query() returned a bare MySQL result
3009          * resource, and it was necessary to call this function to convert it to
3010          * a wrapper. Nowadays, raw database objects are never exposed to external
3011          * callers, so this is unnecessary in external code. For compatibility with
3012          * old code, ResultWrapper objects are passed through unaltered.
3013          *
3014          * @param $result bool|ResultWrapper
3015          *
3016          * @return bool|ResultWrapper
3017          */
3018         public function resultObject( $result ) {
3019                 if ( empty( $result ) ) {
3020                         return false;
3021                 } elseif ( $result instanceof ResultWrapper ) {
3022                         return $result;
3023                 } elseif ( $result === true ) {
3024                         // Successful write query
3025                         return $result;
3026                 } else {
3027                         return new ResultWrapper( $this, $result );
3028                 }
3029         }
3030
3031         /**
3032          * Ping the server and try to reconnect if it there is no connection
3033          *
3034          * @return bool Success or failure
3035          */
3036         public function ping() {
3037                 # Stub.  Not essential to override.
3038                 return true;
3039         }
3040
3041         /**
3042          * Get slave lag. Currently supported only by MySQL.
3043          *
3044          * Note that this function will generate a fatal error on many
3045          * installations. Most callers should use LoadBalancer::safeGetLag()
3046          * instead.
3047          *
3048          * @return int Database replication lag in seconds
3049          */
3050         public function getLag() {
3051                 return intval( $this->mFakeSlaveLag );
3052         }
3053
3054         /**
3055          * Return the maximum number of items allowed in a list, or 0 for unlimited.
3056          *
3057          * @return int
3058          */
3059         function maxListLen() {
3060                 return 0;
3061         }
3062
3063         /**
3064          * Some DBMSs have a special format for inserting into blob fields, they
3065          * don't allow simple quoted strings to be inserted. To insert into such
3066          * a field, pass the data through this function before passing it to
3067          * DatabaseBase::insert().
3068          * @param $b string
3069          * @return string
3070          */
3071         public function encodeBlob( $b ) {
3072                 return $b;
3073         }
3074
3075         /**
3076          * Some DBMSs return a special placeholder object representing blob fields
3077          * in result objects. Pass the object through this function to return the
3078          * original string.
3079          * @param $b string
3080          * @return string
3081          */
3082         public function decodeBlob( $b ) {
3083                 return $b;
3084         }
3085
3086         /**
3087          * Override database's default behavior. $options include:
3088          *     'connTimeout' : Set the connection timeout value in seconds.
3089          *                     May be useful for very long batch queries such as
3090          *                     full-wiki dumps, where a single query reads out over
3091          *                     hours or days.
3092          *
3093          * @param $options Array
3094          * @return void
3095          */
3096         public function setSessionOptions( array $options ) {}
3097
3098         /**
3099          * Read and execute SQL commands from a file.
3100          *
3101          * Returns true on success, error string or exception on failure (depending
3102          * on object's error ignore settings).
3103          *
3104          * @param $filename String: File name to open
3105          * @param $lineCallback Callback: Optional function called before reading each line
3106          * @param $resultCallback Callback: Optional function called for each MySQL result
3107          * @param $fname String: Calling function name or false if name should be
3108          *      generated dynamically using $filename
3109          * @return bool|string
3110          */
3111         public function sourceFile(
3112                 $filename, $lineCallback = false, $resultCallback = false, $fname = false
3113         ) {
3114                 wfSuppressWarnings();
3115                 $fp = fopen( $filename, 'r' );
3116                 wfRestoreWarnings();
3117
3118                 if ( false === $fp ) {
3119                         throw new MWException( "Could not open \"{$filename}\".\n" );
3120                 }
3121
3122                 if ( !$fname ) {
3123                         $fname = __METHOD__ . "( $filename )";
3124                 }
3125
3126                 try {
3127                         $error = $this->sourceStream( $fp, $lineCallback, $resultCallback, $fname );
3128                 }
3129                 catch ( MWException $e ) {
3130                         fclose( $fp );
3131                         throw $e;
3132                 }
3133
3134                 fclose( $fp );
3135
3136                 return $error;
3137         }
3138
3139         /**
3140          * Get the full path of a patch file. Originally based on archive()
3141          * from updaters.inc. Keep in mind this always returns a patch, as
3142          * it fails back to MySQL if no DB-specific patch can be found
3143          *
3144          * @param $patch String The name of the patch, like patch-something.sql
3145          * @return String Full path to patch file
3146          */
3147         public function patchPath( $patch ) {
3148                 global $IP;
3149
3150                 $dbType = $this->getType();
3151                 if ( file_exists( "$IP/maintenance/$dbType/archives/$patch" ) ) {
3152                         return "$IP/maintenance/$dbType/archives/$patch";
3153                 } else {
3154                         return "$IP/maintenance/archives/$patch";
3155                 }
3156         }
3157
3158         /**
3159          * Set variables to be used in sourceFile/sourceStream, in preference to the
3160          * ones in $GLOBALS. If an array is set here, $GLOBALS will not be used at
3161          * all. If it's set to false, $GLOBALS will be used.
3162          *
3163          * @param $vars bool|array mapping variable name to value.
3164          */
3165         public function setSchemaVars( $vars ) {
3166                 $this->mSchemaVars = $vars;
3167         }
3168
3169         /**
3170          * Read and execute commands from an open file handle.
3171          *
3172          * Returns true on success, error string or exception on failure (depending
3173          * on object's error ignore settings).
3174          *
3175          * @param $fp Resource: File handle
3176          * @param $lineCallback Callback: Optional function called before reading each line
3177          * @param $resultCallback Callback: Optional function called for each MySQL result
3178          * @param $fname String: Calling function name
3179          * @param $inputCallback Callback: Optional function called for each complete line (ended with ;) sent
3180          * @return bool|string
3181          */
3182         public function sourceStream( $fp, $lineCallback = false, $resultCallback = false,
3183                 $fname = 'DatabaseBase::sourceStream', $inputCallback = false )
3184         {
3185                 $cmd = '';
3186
3187                 while ( !feof( $fp ) ) {
3188                         if ( $lineCallback ) {
3189                                 call_user_func( $lineCallback );
3190                         }
3191
3192                         $line = trim( fgets( $fp ) );
3193
3194                         if ( $line == '' ) {
3195                                 continue;
3196                         }
3197
3198                         if ( '-' == $line[0] && '-' == $line[1] ) {
3199                                 continue;
3200                         }
3201
3202                         if ( $cmd != '' ) {
3203                                 $cmd .= ' ';
3204                         }
3205
3206                         $done = $this->streamStatementEnd( $cmd, $line );
3207
3208                         $cmd .= "$line\n";
3209
3210                         if ( $done || feof( $fp ) ) {
3211                                 $cmd = $this->replaceVars( $cmd );
3212                                 if ( $inputCallback ) {
3213                                         call_user_func( $inputCallback, $cmd );
3214                                 }
3215                                 $res = $this->query( $cmd, $fname );
3216
3217                                 if ( $resultCallback ) {
3218                                         call_user_func( $resultCallback, $res, $this );
3219                                 }
3220
3221                                 if ( false === $res ) {
3222                                         $err = $this->lastError();
3223                                         return "Query \"{$cmd}\" failed with error code \"$err\".\n";
3224                                 }
3225
3226                                 $cmd = '';
3227                         }
3228                 }
3229
3230                 return true;
3231         }
3232
3233         /**
3234          * Called by sourceStream() to check if we've reached a statement end
3235          *
3236          * @param $sql String SQL assembled so far
3237          * @param $newLine String New line about to be added to $sql
3238          * @return Bool Whether $newLine contains end of the statement
3239          */
3240         public function streamStatementEnd( &$sql, &$newLine ) {
3241                 if ( $this->delimiter ) {
3242                         $prev = $newLine;
3243                         $newLine = preg_replace( '/' . preg_quote( $this->delimiter, '/' ) . '$/', '', $newLine );
3244                         if ( $newLine != $prev ) {
3245                                 return true;
3246                         }
3247                 }
3248                 return false;
3249         }
3250
3251         /**
3252          * Database independent variable replacement. Replaces a set of variables
3253          * in an SQL statement with their contents as given by $this->getSchemaVars().
3254          *
3255          * Supports '{$var}' `{$var}` and / *$var* / (without the spaces) style variables.
3256          *
3257          * - '{$var}' should be used for text and is passed through the database's
3258          *   addQuotes method.
3259          * - `{$var}` should be used for identifiers (eg: table and database names),
3260          *   it is passed through the database's addIdentifierQuotes method which
3261          *   can be overridden if the database uses something other than backticks.
3262          * - / *$var* / is just encoded, besides traditional table prefix and
3263          *   table options its use should be avoided.
3264          *
3265          * @param $ins String: SQL statement to replace variables in
3266          * @return String The new SQL statement with variables replaced
3267          */
3268         protected function replaceSchemaVars( $ins ) {
3269                 $vars = $this->getSchemaVars();
3270                 foreach ( $vars as $var => $value ) {
3271                         // replace '{$var}'
3272                         $ins = str_replace( '\'{$' . $var . '}\'', $this->addQuotes( $value ), $ins );
3273                         // replace `{$var}`
3274                         $ins = str_replace( '`{$' . $var . '}`', $this->addIdentifierQuotes( $value ), $ins );
3275                         // replace /*$var*/
3276                         $ins = str_replace( '/*$' . $var . '*/', $this->strencode( $value ) , $ins );
3277                 }
3278                 return $ins;
3279         }
3280
3281         /**
3282          * Replace variables in sourced SQL
3283          *
3284          * @param $ins string
3285          *
3286          * @return string
3287          */
3288         protected function replaceVars( $ins ) {
3289                 $ins = $this->replaceSchemaVars( $ins );
3290
3291                 // Table prefixes
3292                 $ins = preg_replace_callback( '!/\*(?:\$wgDBprefix|_)\*/([a-zA-Z_0-9]*)!',
3293                         array( $this, 'tableNameCallback' ), $ins );
3294
3295                 // Index names
3296                 $ins = preg_replace_callback( '!/\*i\*/([a-zA-Z_0-9]*)!',
3297                         array( $this, 'indexNameCallback' ), $ins );
3298
3299                 return $ins;
3300         }
3301
3302         /**
3303          * Get schema variables. If none have been set via setSchemaVars(), then
3304          * use some defaults from the current object.
3305          *
3306          * @return array
3307          */
3308         protected function getSchemaVars() {
3309                 if ( $this->mSchemaVars ) {
3310                         return $this->mSchemaVars;
3311                 } else {
3312                         return $this->getDefaultSchemaVars();
3313                 }
3314         }
3315
3316         /**
3317          * Get schema variables to use if none have been set via setSchemaVars().
3318          *
3319          * Override this in derived classes to provide variables for tables.sql
3320          * and SQL patch files.
3321          *
3322          * @return array
3323          */
3324         protected function getDefaultSchemaVars() {
3325                 return array();
3326         }
3327
3328         /**
3329          * Table name callback
3330          *
3331          * @param $matches array
3332          *
3333          * @return string
3334          */
3335         protected function tableNameCallback( $matches ) {
3336                 return $this->tableName( $matches[1] );
3337         }
3338
3339         /**
3340          * Index name callback
3341          *
3342          * @param $matches array
3343          *
3344          * @return string
3345          */
3346         protected function indexNameCallback( $matches ) {
3347                 return $this->indexName( $matches[1] );
3348         }
3349
3350         /**
3351          * Check to see if a named lock is available. This is non-blocking.
3352          *
3353          * @param $lockName String: name of lock to poll
3354          * @param $method String: name of method calling us
3355          * @return Boolean
3356          * @since 1.20
3357          */
3358         public function lockIsFree( $lockName, $method ) {
3359                 return true;
3360         }
3361
3362         /**
3363          * Acquire a named lock
3364          *
3365          * Abstracted from Filestore::lock() so child classes can implement for
3366          * their own needs.
3367          *
3368          * @param $lockName String: name of lock to aquire
3369          * @param $method String: name of method calling us
3370          * @param $timeout Integer: timeout
3371          * @return Boolean
3372          */
3373         public function lock( $lockName, $method, $timeout = 5 ) {
3374                 return true;
3375         }
3376
3377         /**
3378          * Release a lock.
3379          *
3380          * @param $lockName String: Name of lock to release
3381          * @param $method String: Name of method calling us
3382          *
3383          * @return int Returns 1 if the lock was released, 0 if the lock was not established
3384          * by this thread (in which case the lock is not released), and NULL if the named
3385          * lock did not exist
3386          */
3387         public function unlock( $lockName, $method ) {
3388                 return true;
3389         }
3390
3391         /**
3392          * Lock specific tables
3393          *
3394          * @param $read Array of tables to lock for read access
3395          * @param $write Array of tables to lock for write access
3396          * @param $method String name of caller
3397          * @param $lowPriority bool Whether to indicate writes to be LOW PRIORITY
3398          *
3399          * @return bool
3400          */
3401         public function lockTables( $read, $write, $method, $lowPriority = true ) {
3402                 return true;
3403         }
3404
3405         /**
3406          * Unlock specific tables
3407          *
3408          * @param $method String the caller
3409          *
3410          * @return bool
3411          */
3412         public function unlockTables( $method ) {
3413                 return true;
3414         }
3415
3416         /**
3417          * Delete a table
3418          * @param $tableName string
3419          * @param $fName string
3420          * @return bool|ResultWrapper
3421          * @since 1.18
3422          */
3423         public function dropTable( $tableName, $fName = 'DatabaseBase::dropTable' ) {
3424                 if( !$this->tableExists( $tableName, $fName ) ) {
3425                         return false;
3426                 }
3427                 $sql = "DROP TABLE " . $this->tableName( $tableName );
3428                 if( $this->cascadingDeletes() ) {
3429                         $sql .= " CASCADE";
3430                 }
3431                 return $this->query( $sql, $fName );
3432         }
3433
3434         /**
3435          * Get search engine class. All subclasses of this need to implement this
3436          * if they wish to use searching.
3437          *
3438          * @return String
3439          */
3440         public function getSearchEngine() {
3441                 return 'SearchEngineDummy';
3442         }
3443
3444         /**
3445          * Find out when 'infinity' is. Most DBMSes support this. This is a special
3446          * keyword for timestamps in PostgreSQL, and works with CHAR(14) as well
3447          * because "i" sorts after all numbers.
3448          *
3449          * @return String
3450          */
3451         public function getInfinity() {
3452                 return 'infinity';
3453         }
3454
3455         /**
3456          * Encode an expiry time into the DBMS dependent format
3457          *
3458          * @param $expiry String: timestamp for expiry, or the 'infinity' string
3459          * @return String
3460          */
3461         public function encodeExpiry( $expiry ) {
3462                 return ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() )
3463                         ? $this->getInfinity()
3464                         : $this->timestamp( $expiry );
3465         }
3466
3467         /**
3468          * Decode an expiry time into a DBMS independent format
3469          *
3470          * @param $expiry String: DB timestamp field value for expiry
3471          * @param $format integer: TS_* constant, defaults to TS_MW
3472          * @return String
3473          */
3474         public function decodeExpiry( $expiry, $format = TS_MW ) {
3475                 return ( $expiry == '' || $expiry == $this->getInfinity() )
3476                         ? 'infinity'
3477                         : wfTimestamp( $format, $expiry );
3478         }
3479
3480         /**
3481          * Allow or deny "big selects" for this session only. This is done by setting
3482          * the sql_big_selects session variable.
3483          *
3484          * This is a MySQL-specific feature.
3485          *
3486          * @param $value Mixed: true for allow, false for deny, or "default" to
3487          *   restore the initial value
3488          */
3489         public function setBigSelects( $value = true ) {
3490                 // no-op
3491         }
3492
3493         /**
3494          * @since 1.19
3495          */
3496         public function __toString() {
3497                 return (string)$this->mConn;
3498         }
3499 }